Just remember using mods that compliment each is important. Some mods will make more power individually when coupled with another. Like exhaust and intake. If exhaust gives you X hp and Intake Y hp together they should produce more than just x+y.

And the engine is not the only place to gain some Hp. Some of the 3.8V6 fbody guys see swap out the torque converter to lower some of the drive loss, and get some redistribution of the torque at the wheels.
I'm not sure what gears the crossfire comes with stock. But sometimes its with the less gas mpg for a more aggressive rear gear. Not to mention lighter drive components, flywheel, driveshaft. Also you might be able to find some aftermarket wheels that look nicer and weigh less. Lighter wheel will defiantly give you a faster ride. Some of those things might not be crossfire specific and could be found as a Merc mod.