I've never heard of anyone pushing the 2.5 or 2.8 to 300hp without F/I.
Until recently only the ODBI cars (2.5) were capable of putting out huge HP numbers, now that tuners have finally mastered OBDII (2.8) you're seeing the same numbers as the OBDI cars
I don't know what that translates to in terms of price differences though.
If your going FI, and on a budget, I'd venture to say buy a cheaper 325 and invest the rest in the kit. If deep down your know your full of hot air and FI isn't gonna happen, get the 328