I'm thinking the same thing you are. I've pretty much ruled out the RBs because the price has been inflated by everyone doing the 240sx swap. $2500+ for a rb25det? no thanks.
From what I've read on this site, 450hp on the l28et is asking a lot, while it seems to be common for the other motors to do that and more.
I've read a lot of good things about the 7m-gte (take Clifton's Z for example) but it has issues. One of the probs with that motor is that the engine has a notoriously bad headgasket design. So most people get the block machined so they can use a metal headgasket. From what I've read on supra forums, there's also a problem with rod knock, so take that into consideration as well.
Also, I think past 300-350hp you have also have to go piggy-back fuel system which gets messy. Meqasquirt is an option, but there's not many ppl running it and since the motor uses coilpacks and no dizzy, that gets kind of messy as well. I don't know much about any other management systems because they're $$.
Recently I've been looking into the 1jz-gte, which runs around $1200-1600 for a complete engine and makes around 280hp stock on 2 small twins. I haven't come across many downsides to this motor and it's really starting to sound good. But I haven't done extensive research yet.
So as it stands now for me, I'm leaning towards the 1jz-gte because it matches my goals.