To keep close to your price range I would check out the JBL BP600.1. It will give you some pretty decent power for your subs and prevent you from spending a whole lot. You can get these for just over $200 brand new if you look hard enough. I know there's a few online stores that sell them around the $250 range.

You probably won't need a capacitor and they're not always the solution to power problems anyway. Also when you get your amp kit.. I'd say go ahead and get a 4 gauge kit. 8 might be a little low for you and 4 ga will def. be fine and allows you room to upgrade in the future.