The amp you need really depends on what you want to do with you system. If you know your not going to expand your system or add any more speakers or subs then you can go with a mono amp. However, I like to go with multi-channel amps. This gives me mo...
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.
2 channel can run a left and right speakers=2 pos and 2 neg connections. multi same exept in how many channels it has 2,4,5. mono amp is a sub amp only 1 pos, neg connection. but can have 1+ subs depends on ohms the amp is rated at and ohms of subs