If V10 was in there, that'd take it - it was a very very easy option not having 4cyl in there though between turbo 6 and ANY V8 was a bit of a hard one. I've found a pattern, if I am at an event with a bunch of angry turbo 6s and then hear a nuts V8 (ie, drifting) it makes me very very happy.... but then if I am at an event with heaps of angry V8s and then hear a nasty turbo 6 (ie, drags) then that also gives a special shiver up my spine.
I'm going to go with turbo 6s virtually at the flip of a coin, I guess I *own* a turbo 6 (RB25DET) and I absolutely love the way it sounds even after years of driving it and I can't bring myself to let it go... so am going to further develop it. A very nicely developed RB or 2JZ both sound completely amazing, slightly different equalities but still awesome.
I don't agree with RB26s being the only ones sounding good either, its easy to think so after all the rough as RB20s/RB25s running around but any of them played with right can be pretty sweet. Hell, even Buick V6s can sound impressive!
http://www.youtube.com/watch?v=w_OE3GLYac4