I would suggest Googling to find out more info on amplifiers, but here is a link that has some good overview information on amplifier fundamentals:
http://rocketroberts.com/audio.htm. See the 'Power Amplifier Fundamentals' and 'Audio Power Amplifier Power Rating Mysteries Explained' articles.
To answer some of the questions:
- A Monoblock is a one channel amplifier. If you use all monoblocks you would need one for each channel.
- Amplifiers come in multi-channel variations: 2, 3, 5, and 7 channels.
- You can use any combination of amps, like a 2 channel amp to drive the front left and right speakers and a 3 channel amp to drive the center and surrounds or a single 5 channel amp to drive them all.
- You can use a receiver as a pre-amp as long as it has amplifier pre-outs. Most receivers over $500 have pre-outs. You can use all of the pre-outs to feed a single 5 or 7 channel amp or again mix and match amps. Many people like to use only the front L and R pre-outs to a 2 channel amp to drive the fronts and let the receiver drive the other channels. If convenience and space are considerations, its better to use a single multi-channel amp rather than having multiple amps.