Gotcha. Well, if I were going for a simple 4 channel amp upgrade to power the front stage, I'd go with the Sony XM-4S; link
Search around, you should be able to get it around 100 bucks.
I like it because you can fit it where the factory amplifier goes (behind the driver-side rear quarter panel), or you can tuck it behind the passenger-side rear quarter panel. It's literally the size of a large hand... makes for such a clean, factory-looking, install.