2530 turbo won't give you heaps more top end than the stocky but will give you a shit load more midrange. Expect around 220rwkw at the wheels. 2535 will give you an easy 230-235rwkw with again some good midrange as well. Either turbo is good, i had both on mine.
If you want higher dyno numbers , check one of the other turbo, GCG's etc, but havent seen any beat my 1/4 mile with the little HKS yet.