problem with the RB20 is you loose heaps more torque the more power you seek.
if your wanting big gains you'll also get losses where it counts, 250 is a max limit you want to go for, but i wouldnt recommend going any higher then say a HKS2530, 2530, or 2540.......wouldnt mind seeing the results on a 2835 in RB20.
i dunno, its your call.......but unless your willing to increase capacity to say 2.4 ltr or something along those lines, you'll lose some goodness, personally i was happy with my VG30 on the RB20