if you do go down a size, only go to a 3.4... The intercooler is a great investment, I have the S2 from zzp and love it (dont get the short stack its a waste of money). But with just an IC, its really not gonna do a whole lot for your car until you get some flow mods (exhaust, cam, rockers, etc...) so I wouldn go that small in pulley size...

and another thing you should get is a scan gauge now in case your IC pump fails so you can see the KR....