Originally Posted by Fabrik8

Get a 6 channel amp and a sub amp, or 3 amps. The amps for the main speakers are going to be fairly small so I don't think installation will be a problem. You can match the amp power to the size of the speakers, so if you have little 4" speakers you could put 35 watts instead of something like 50 or 75 watts for a larger size speaker. Basically you don't necessarily need 6 amps channels with 75 watts each, so the amps might not add up to be physically very big (if that makes sense..).

I'd say get a 6 channel if possible though, that way you'll have the most compact installation possible, or you could install the amps in different areas if you need.

I'd take a look at the dimensions of whatever amps you're interested in, and see if they'll fit where you want them to go. Looking at the link to the JBL amp above, it appears that a 4 channel and a 2 channel amp might take up less room than the JBL 6 channel, but I could be wrong..

As far as the wiring, a cap isn't necessary on anything but the sub amp. The other amp(s) aren't going to be drawing the same peak current loads as the sub amp will, so don't waste your money. Install the cap as close as possible to the sub amp, just like normal.
A distribution block is the easiest way to distribute power and ground, yes. The ground block will be non-fused (obviously), but the power block should have a fuse per output (which also makes it easy to pull a fuse and shut off an amp for tuning or troubleshooting).

If the amps are in different locations (not very close to each other) you can use a fused distr block for power but you should ground the amps to the chassis where they are installed, instead of running long grounds back to a central distr block..