What amp?
Look at some factory refurb'd Kicker ZX700.5's.. plenty of power for the doors, AND a mono subwoofer amp, in one easier to install package. It's in your price range.
I prefer refurb stuff alot, because it means that it's actually been checked out by the factory, and not maybe 1 in 100 like the "new" stuff.. An amp should last damn near forever anyway.
I'm a big fan of 5 channel amps, it makes things SO much easier.. one physical installation, one power wire, etc, etc..

