What size is the bar? If it's 22mm or smaller, the stocks are probably fine. If it's adjustable to a larger size than 22mm, then new mounts are worth it.

 

I assume you're referring to the perrin solid pillowball endlinks (let me know if you're not). I have these, and they seem to provide a nice crisp response, but on my car they are noisy as all get out.

TANSTAAFL.

 

I have a Cusco set to 23mm in rear on stock mounts. No problem for 6 months. Stock mounts shuld be ok for most conditions, but if you are planning to do a lot of track/autocross then you may need beefed-up mounts.

 

it think getting aftermarket ones do make a difference, to me the stock ones are not stiff enough, they are plastic and seem like they deform very easily. i personally have the solid helix endlinks and am glad i changed from the stock ones

 

I think smithEr is asking about mounts, not links. The mounts are ok up to 22-23mm, street use. For heavier bars and heavier use get reinforced mounts. Stock mounts sometime can break due to stress concentrations and fatigue around the holes.

Solid endlinks are not really all that necessary. I have Kartboys, they are good, but they dont doo too much. The only advantage is that they are more linear and more compliant than the stock plastic ones.

i'd stay away from pillowball/uniball links though; too noisy and the sway bar will walk. Kartboy/Whiteline are good.
http://www.subaruwrxparts.com/per-wrx-suspension.html

 

my bad, i mis read the post

 

smithEr, correct torque is important (should be around 25-30 in-lbs). Urethane bushings squeak, especially when they get dry or cold. Plenty of grease is needed, or teflon tape. I am lucky to have Cuscos which use rubber and dot squeak.