It's not really about Max HP it's more about how much money do you want to spend and how much HP do you want? As far as i'm concerned with enough money you can have whatever HP you want (realistic) in whatever car you want.
If you just wanna check out stuff for your car, check the forced induction section they have stickies with peoples mods and power output, or cruise around the parts suppliers websites, HKS, Apexi, Tomei etc.
Personally I am currentley makin about 400hp at the wheels, if I wanted to bump it up to 600 say I would have to go to aftermarket turbos and a bigger fuel system.....more to the point you need numbers to aim for