No right channel or sub

Well, phooey. My install seems to have some issues lately. I seem to get no sound(*) from the right sight of the car, or the sub. I have a pretty simple setup -- empeg is the only HU, feeding into a) a 4 channel amp, and b) a 2 channel amp for the sub. First thing was to check that all amp fuses passed visual inspection. Then, before tearing the dash apart, I figured I'd check the RCA connectors on the amps, and see if the empeg is at least getting a signal to the amps. Every RCA connector registered the same voltage levels (positive lead on center of connector, negative on ground), between .5V and 1V (depending on the track, of course). Then I checked the outputs from the amps (positive on a +ve or -ve lead to the speaker, negative on ground). All of them were about .4V. Is my logic correct in assuming then, that the problem is between the amps and speakers, then?

In doing this checking, I noticed that the right front -ve lead wire had pulled out of the crimping thing. After reseating that, nothing changed. Could that have caused any other permanent widespread mayhem?

(*) where "no sound" is defined as nothing audible from a regular listening position, but if my ear is pressed up against the speaker, I can make out some faint attempts at music.

Swap the left and right RCAs at the amp. Does the problem stay on the right or does it follow the RCAs?

Great suggestion. I just tested that, and the audio comes out of the same speaker as before, but nowhere else. At least that means I am getting a signal on both left and right, so it's not the empeg or behind-the-dash wiring. Hmmm... I really hope I don't have to go into amp replacement mode.

Well, swap the speaker cables a the amp now. If it stays on the same side, it's the speaker. If it swaps, it's the amp.

*sigh* I don't know why I didn't think of doing this as a logical extension of your first suggestion. Maybe because I have to take the seats out of my truck to do so. Regardless, For this, I'll let you get away with your tabbing habits.