Photo shopped GTO or not I think it'* a sweet looking concept for a ride. The original GNX is still a car I'd love to have, my wife thinks it'* ugly and looks like a drug dealers car though. If a new one came out looking like that she'd probably want one more than I already do.
As far as getting the power out of a 6, why not? There'* guys cranking 600hp out of 2.2 4cylinder S10 pickups. I don't know anything about this 3.6 but with GMs 3.9 putting out 240 stock and without a super charger, think about what it could do with a little tweaking and a (yes maybe even twin) super charger.