whats "cheap" to you? an orion 8004 is a fairy reasonable priced amp, and will put out a lil more than that. head room is always good, just set the gains accordingly
or if your cheap is MY kind of cheap, you might look at the Lanzar Vibe 431, or Power Acoustik/SPL both make some powerful 4 ch's that aren't too bad on a budget.
oh sorry bout that... erm... something around $200 - $300... but cheaper would be great... erm... a decent amp will do... but must be around the 80 - 90 watt per channel...