I had a HKS 2535 which is a little better but I have been in an RB25 with a 2530 on it and there is almost no lag! It was an awsome street car the only downfall it had was that you couldnt push it to redline you were better of shifting at 6 - 6,500 rpm...
I would do it.. it will make about 220 - 230 max but i have seen them run mid 12's in an R33.. PM Robo's on the forum, he had one.
Its not all about rwkw.... from how laggy you have said your turbo is, the 2530 would destroy the kkr setup on the street even if it was making a bit more power.