If you have a good head unit then i would recommended using a Fosgate AMP. I have a Rockford Fosgate amp in my car and it delivers a thumping bass and pretty good power. When buying a amp make sure that you change the speaker wires and the speakers to match with the amp.
For example.....fosgate has a 4 ohm output impedance. So any speaker that you buy should be rated at 4 ohms in. This will give you a good matching with the amp.
Ps: Before conforming that the amp is dead i think you should test it with a phantom load or check the power source with a multimeter.
Hope this helps
Jake Miller
Toyota of Santa Monica