well ive got a single HKS2530 (with slightly less flow than the 2535) mine can flow about 320ps according to HKS but ive already got close to 300rwhp out of that on my RB20. so if you have two 2535's according to HKS you will have like 700ps of huff.
But like boosted RB26 said, you will need, computer, injectors, cooler, exauhst, clutch, and metal headgasket to start making serious power. my friends 32GTR has only highflowed turbos and metal headgasket, cooler and exaust and is making 410rwhp (300rwkw) on 12psi of boost.
so the 2530's are a much better turbo and should produce alot more power, and capable of running pretty high boost.