i have a predator, it will give you some HP and TQ. i did not do a dyno tune fir just the predator so i dont know what the numbers are. But i think its usefull. You can use it to read codes and change things like your gear ratio, rev limiter, govoner (if you have one), adjust for bigger tires, advance or re tard timing etc etc...You prob alredy know all this though.
Honestly you can feel some more hp/tq after you install, but its NOT a huge increase. Well i should say I didnt not feel a huge increase. Each car is diff.
With just the mods in your sig, the base tune from a Predator or Xcalibrator2 will be felt. Both will net you about the same. Go look at the features of both, upgradability, support, and pricing then decide. There are many many threads on that here. Good luck.