First, let's make sure everyone understands what an ohm is. An ohm is a unit of measure that measures resistance to current. So a speaker doesn't "run" at any ohm. It puts a load on the amplifier. So, a speaker puts a certain amout of resistance or load on an amplifier.
Second, good luck finding an amplifier that really is 1 ohm stable. There aren't very many. Then to make a long story short, when you make an amp run at 1 ohm, sound quality diminshes a little bit. I highly recommend you keep most amps at a 2 ohm load or higher.
Third, when you wire up your four voice coils you can end up with a final load of either 1/2, 2, or 8. That's it. I can teach you the math later. An amplifier has no idea how many speakers you have. It doesn't care either. What it does care about is the load that the speakers put on it. So on a one channel amplifier, those are the loads you will present to the amplifier.............. With a two channel amplifier, you should bridge the amplifier. When you do this, each rail (channel) basically "shares" the load. That means the load presented to the amplifier will be half of what the speakers load is. One example that illistrates this would be an amplifier that is stable to 2 ohm stereo or 4 ohm mono (bridged). Because when it's bridged, the (rails) channels "share" the load. So, for the speakers that you have, I wouldn't recommend a 2 channel amplifier.
Fourth, this is recommendation is my opinion...... If you don't share it. I don't care. I know that a one ohm stable amplifier (2 channel) would be great for this system.