Cartman,
I don't think you can do it the way you're thinking. Let's just think about one speaker for a minute. Normally you would use one amp. No problem. Everybody knows how to do that. Some people, if they have a 2-channel amp, want to bridge the amp so that both channels are combined, which would double the amount of power into the one speaker. When you bridge an amp, you're doing nothing more than telling one channel (let's say the left channel in this case) to operate on the positive half of the waveform and the other channel (which would therefore be the right channel) to operate on the negative half. Voila! Your 2-channel amp is behaving like a 1-channel (mono) amp and you're getting double the power. Notice however, that both channels are not operating on the same part of the waveform at the same time. They are splitting responsibility - I'll work on one half and you can work on the other half.
The way this relates to what you're asking, is that the only way I know of that you can get two separate amplifiers to operate properly on a single load (either one speaker, or multiple speakers tied together), is if you can duplicate what you would get if you bridged two amplifier channels - one amp would need to operate on the positive half of the waveform and the other amp would need to operate on the negative half. Amplifiers don't automatically know how to do this. They need to have this feature built in. This is what Mhn3773 is referring to with the 4 amps. Kicker makes some amps that have what is called a strapping connection. Strapping is nothing more than bridging. When you connect the strapping jacks on 2 amps with this feature, each amp will work on the corresponding part of the waveform and not interfere with the other.
So in summary, to do what you want to do, you need two identical amps and they both have to have a "strapping" feature.