3.8 Should I buy a two or four (or more) channel amplifier? [JSC]
If you only have one line-level set of outputs available, and wish to power two sets of speakers from a single amplifier, you may be able to save money by purchasing a two channel amplifier which is stable to two ohms rather than spending the extra money for a four channel amp. If you do this, however, you will be unable to fade between the two sets of speakers (without additional hardware), and the damping factor of the amplifier will effectively be cut in half. Also, the amp may run hot and require fans to prevent overheating. If you have the money, a four channel amp would be a better choice. You would need to add a dual-amp balancer in order to maintain fader capability, however, but it is more efficient than building a fader for a two channel amp. If you wish to power a subwoofer or additional speakers as well, you may want to purchase a five or six channel amp.
CAF comment: We have had great success using a good quality 4 channel amp to power front and rear speakers along with a pair of subs on the back channels. But with the added multimedia use (surround sound AC3 / 5.1) with large video systems, seperate channels for front and rear are needed.