2 seperate amps for sure..... that way you arent restriced to the same frequency... i would go with a 2-channel amp (that has around 300 rms) then i would go with a mono block or a 2-channel amp that pushes at least 1200 watts (600 per channel if its...
2-channel amps are designed for two speakers and 4-channel amps for 4 speakers. You can usually bridge a 2-channel to one and a 4-channel to two channels. This will half the impedance of whatever the speakers are.
Check the manual. If you don't have one, check the website. Not all amps are the same, especially if your amp is a few years old. I have had an amp that was wired #2, however #1 is pretty common these days. I have never heard of choice #3, but I can'...