Eh either way. With me its never enough, so who knows how long I'll stay on the stock turbo even haha. I'm already trying to decide of meth is worth the effort.
The thing I like about the Cosworth's is they show gains throughout the entire rpm range. You might get better peak hp out of the GSC's but the dyno plots I saw show they don't run as consistantly over the rpm range as does the cosworths. Maybe the dyno's I saw weren't tuned well or something, but coming from an s2000 I like nice smooth gains right up to redline.
My s2000's power curve looked like this / up to 9000rpm. After I got the SC'r it was even better

. Sometimes I really miss that car sigh.