Subaru actually makes a Subaru -S gear oil my friend switched over to that in his 07 WRX TR and loves it. i drove his car around and agreed it's good.
I think he bought a gallon or two of the stuff. he had some metal bits come out of his transmission the first time he changed his fluid (org fluid at like 10k miles) so he wanted to flush out his tranny a few times. (hence buying a few gallons) Anywho the stuff works great (and it's even from Subaru) its their S gear oil or super S ... it has S in it. probably the suff they use in the STI. I've also used red line in my rally car.. works good too.