Hey David, that'll depend on what you want to with it. Do you want to power your subs or all of the speakers in your car? For the subs, you'll need to get at least 500W rms amp that's 2ohms or 1ohm stable. If you're planning to power your 6x9's and 3inchers, then a 4 channel amp would be a good idea. Look for something that's 75w rms x 4 at least.
What size amp do i need if I want to power a 15 inch jl sub