Audio stereo problem

[Lrhull4]

Who's the audio specialist? So my stereo speakers started months ago cutting out intermittently sometimes the right sometimes the left sometimes the little tweeter in the A post. Back always worked. But now I'm down to just having a left door speaker. Question is it the stereo, speakers or amplifiers hooked to the speakers? Has anyone had this problem? I thought I'd put in a new stereo but then it had no sound then I found out about the whole amplifier thing powering up I don't want to wire it up correctly if the amps are bad in the first place. So now I'm back trying to figure out what's not working in the first place. How do I test the amps. 2001 ram 2500 cummins.