Wiring 2 amps to the stereo

I have been given 2 amps and 2 speakers - I want to put them into my
car. I would like to use both of the amps - just to make it as loud as
possible. This is my first time doing anything like this with my car.

The amps a
Spider 6800 MacAudio - 680W
BoschMann Pch-2500Fx - 300W

My car stereo is a RipSpeed DVD722B.

I have tried wiring one speaker to one of the amps and the other
speaker to the other amp. However only one speaker will sound. Each of
the parts seems to work individually.

Are there any circuit diagrams that can help me, do I need any more
kit?

Thanks

Robert