hey mate just a couple of things.
have you already bought the car if not i could import you a real wrx from aust with heaps of mods or standard for the same price you have been quoted and i can get you anything from a 96 model to a 2000 model for around that price.
i saw a 96 model recently which had a dog box and about $20,000 dollars worth of mods for only $19,000 aussie dollars.

one other thing you will find you will not get more than one mountain run if that and you will have smashed that rs box as they are way weaker than a wrx box so if you do buy it and you want to do uphill racing which the subaru was never designed for well the gear boxes weren't any way, you will need a dog box for your first mod or at the very least a set of ra sti internals.
trust me on this mate as i smashed my box on the only hill climb i ever did and will never do one again in a subaru even though i have a stronger box they just dont like constant pressure on the box.
i hope i have helped you in some way as i would hate to see you go through the expense of rebuilding your box a couple of times.