Otherwise, I'll just re-iterate one original questions and see if we can get some thoughts on that:
What can he expect from his current engine as far as maintenence/reliability? ("I currently have a 2008 WRX 4EAT ...lots of upgrades and goodies added, but not much on the engine...intake, cat-back exhaust, pro-tune.")
Important to know for anyone to give feedback on that: How many miles are on the car?
As far as whether the Ralliart will be comparable to the WRX with similar mods, as mentioned there's only 1 or 2 guys on this board who have/had Ralliarts, so this may not be exactly a font of info on that question.