At first i wasn't going to post this, as you stated that you wanted to reach 300rwkw, but felt that i should after reading the recent posts.
I am currently in the process of modifying my rb25, roller bearing, hi-flow turbo, by replacing the ext. housing with one off a VG30 turbo (slightly larger than the std. rb25 ext. housing). I am also installing a pair of Tomei PonCams and porting the head. I have read and received various PM's from forum members that have used the same combo, minus the porting, and have acheived approx. 270rwkw with the same response of a std hi-flow. I have already instucted my mechanic/tunner to keep the tune safe and not push the eng, as it still runs the std. bottom end. So i will limit the power and be VERY happy at about 260rwkw. (Note: i believe 270-280rwkw is acheived using 18psi)
The best thing about this combo is that it still looks std. Apart from the fuel pressure reg (but still does not stick out like a sore thumb) and the straight swap 550cc inj, the whole package looks factory.
Hopefully this hasn't confused you more in your decision, but if others are looking at 250-280rwkw than i beleive this combo will be best choice while still appearing std. Remember "stealth" is your friend