Marco.........no question the Z06, 7 liter engine will have much more potential. A 500HP engine at the flywheel in a bone-stock factory car with 3-year warranty is impressive enough. You can certainly do more to it.
Here's an example of fairly easy enhancements on the std. LS2, 6 liter in a regular C6 with 400HP at the flywheel. These guys are already near 500 RWHP without taking the heads off. Chassis dyno results and simple mods done are posted in the thread below:
http://forums.corvetteforum.com/show...26&forum_id=74