*STi Performance Stage5 Kit 'With Cats' $19,499.99 + shipping (Does that include the car?)
(Approximately 450H.P plus)
Please note, all power outputs stated are only approximations, for reference purposes and will vary depending on each vehicle, its condition, fuel and modifications.

SMT PIGGY-BACK ECU: The SMT 'piggyback' ECU is designed to correct fueling and timing. The SMT offers the ability to switch between two tuning maps for different octane fuels and performance, at the touch of a button. This is a wire in unit that can be sent to meet the needs of your car. The SMT is simple to install, (must be soldered in) and includes wiring diagrams, and installation instructions. The SMT can be programmed by any professional tuner, using the 'tuning cable' and software provided in the SMT kit. SMT comes with an OEM base map, which requires custom tuning for this kit. We recommend seeking a professional tuner for installation and tuning.
What I'd like to know is what is Perfect Power's, aka Digital Data Systems, aka Digital Technology from South Africa consumer satisfaction record. That and for $1300, how is it better than other piggybacks?

Also, why, if the SMT controls boost would you need a....

Manual Boost Controller
-save $125
Short Ram Intake: Using the same design feature of the velocity stack found on the inlet to the MAF sensor in the factory box this cast aluminum intake carries the velocity stack radius outward to mate up with a 4.5" high flow cone filter.
I don't think you'd need this, and further, it would most likely cause more problems than it's worth. -save $230
Intake Elbow: Direct replacement for the factory inner fender silencer. Greatly reduce the overall volume between the front intake duct and factory filter box. Made of Thermoformed ABS plastic in order to maintain OEM quality and appearance. Direct bolt-in to factory location.
Again, I don't think you'd need this, and further, it would most likely cause more problems than it's worth. -save $80
Blow Off Valve: Features a “dual” exit system. The Dual Exit system routes roughly 50% of the air back to the Factory Recirculation pipe and 50% of the air out a Billet machined horn. In effect the valve is a Bypass and a Blow off valve in one unit.
You know you wouldn't need this. At least I don't think so. -save $325
High Output 255 liter fuel pump
You would need this, but if you bought it yourself, it isn't very difficult to install.
Adjustable Fuel Pressure Regulator
You definitely wouldn't need this. -save $300
Parallel Fuel Rails
Don't need this. -save $450
*STi Stage3 DOHC Cylinder Head Package: Custom Stage3 STi VVT cams with a 0.419 inch lift for both intake and exhaust, and duration of 235 degrees at 0.050 Lift. Custom Stage3 ported and polished heads. *Price does not include shipping, duty and Core Charge of $5,000.00. Please be patient, each head package is made per order and takes about 8-10 weeks to deliver. Your core charge is refundable if you have returned your OEM heads and cams within 45 days from the date of order delivery, to our designated receiving department and must be received in good, reusable and rebuildable condition, based upon our evaluation. All shipping is the responsibility of the customer. The heads and cams are available on an exchange basis only and is not available for direct sale. Please be patient.
I can't dispute this. I am fairly certain that if you're expecting 750hp at the crank, oem port size and oem valvetrain hardware wouldn't cut the mustard, but again, I haven't heard much in the way of satisfied customers' reviews that would lead me to believe their headwork is an industry leader. I have to assume that they don't machine the heads themselves, so it would certain help to know who their contractor is. I'm guessing it's probably a very familiar company like DPR. Lastly, the whole 'core refund' thing always confused me, but $5k???
Large Top Mount Intercooler: Dual intercooler inlets take full advantage of the intercooler's size by evenly distributing the air across the bar- and-plate core for more efficient cooling, while the large cast alloy end tanks distribute heat evenly across the intercooler and aid in smoothing air flow. Massive bar and plate construction reduces pressure drop over stock allowing the turbocharger to spin slower while producing the same boost pressure in the intake manifold. Not only will this prolong turbocharger life but will also reduce the air temperature exiting the turbocharger, effectively increasing intake charge density.
The oem top-mount is actually rated pretty high, but I don't think it could manage 750 crank hp. Actually, I don't know if any top-mount could. However, if you felt a top-mount was sufficient, I'd recommend buying a good, used Hyperflow v2 and installing it yourself. -save $1025
Equal Length Headers and Uppipe Combo: Designed to significantly gain horsepower and torque.
It may be designed to add 600hp all by itself, but headers are yet to be proven. I opted for a header/uppipe combo, too, but I did it more as an experiment because I don't know what to expect...and I got a killer deal. -save $800
Xcceleration 3" Turbo-Back Exhaust System with Two Cats and exhaust cutout with electric switch: Our Turbo-back Exhaust System features the newest technology in Super Hi-Flow Catalytic Converters and Exhaust Piping. Air flow is increased dramatically to greatly increase your HP and Torque. Our System is a constant 3" pipe size, which retains low end torque and produces high air flow capacity. Our Super High Flow cats flow over 502 cfm, increasing exhaust flow which reduces backpressure. Backpressure forces exhaust gases back into the combustion chamber and contaminates the next burn cycle. Reduced backpressure increases exhaust scavenging from the combustion chamber giving you a cleaner, more efficient burn. The increased momentum of the exhaust pulls more air/fuel into the cylinders, hence increasing low end torque.
I'd imagine that you most likely already have a turbo-back. -save $1600
Billet Rods AND Custom Ultra Light Forged Pistons: Ultra light (374 grams) forging features a strutted crown that provides additional strength for extreme power applications and uses slipper skirts for reduced friction at high rpm. Additional features include, a valve relief trench which increases flow at low valve lifts. As with all proprietary piston designs, quench area is maximized, dramatically reducing detonation and creating a rapid burn combustion chamber which allows for higher boost and higher compression ratios.
I highly recommend upgrading internals. However, don't they state that they're using CPs?
T-Sleeves for EJ25 (99.5mm) able to handle up to 50psi: The T-Sleeve's unique three dimensional support design eliminates sleeve movement under extreme dynamic load. Using the T-Sleeves in your engine reduces the chance of side loading commonly experienced with non-supported conventional sleeves. Sleeve movement under extreme load conditions is the leading cause of head gasket failures.
I can't dispute the need for sleeves, but my feeling is that sleeving is why they're so confident the engine will produce 450hp PLUS. There hasn't been anyone (at least non-professional racers) on any of the Subaru forums who've had this done that I know of. What I'm saying is beyond the sleeving, you could have all of the rest of this package for probably a third of Xcceleration's price. I called a company called Darton East, in New Albany, Indiana and if I recall correctly, they told me that they could sleeve my block for $3k or $4k. Hard to say.
COMETIC Head Gaskets: Cometic's MLS (Multi-Layer Steel) Gaskets are constructed of two nitrile coated outer embossed spring steel layers with a steel inner layer that provides support to the gasket allowing multiple thickness. Cometic gaskets withstands the shearing forces created by aluminum heads on cast iron blocks. Once the gasket takes a torque set, there is no re-torquing required. Less clamping force is required allowing for reduced bore distortion.
I believe Quirt Crawford recommends oem headgaskets. -save $140
Head Stud Kit: This kit is VERY strong (much better than standard) and is suitable for street, race and rally engines which run high boost.
Can't fault that. I opted to use ARP, but I've read a few places where some folks recommend oem.