I don't see why the S65 would be a "downer". it's lighter than the S54, and that weight would sit further back too. and it's maybe more reliable.
A 490whp S54 though.. yikes! How wide would the powerband on that be? 100rpm? :p
the S54 seems to be pretty de-tuned from the factory, I imagine that although the S65 is closer to the edge, it's still considerably de-tuned as well. With nearly a liter more displacement to start with, I imagine it would be considerably cheaper to get to ~500hp with a race setup.
I really like both engines, though. if I had a different car, I'd probably do the S65, but the S54 is my motor of choice..
Last edited by hassmaschine; 08-08-2012 at 08:06 AM.