First question, are you going to run these straight off of an amp or do you intend on having volume controls in each zone? A rcvr with zone 2 pre outs will do what you want to as long as you do not power the 8 zones using the amplified zone 2 outs. The amp in the rcvr will die a very quick death! =)
If you go with volume controls (VC's) make sure they are impedance matching. That way it makes wiring to an amp easier and safer for the amps. With 8 zones I would slip it up into 2 amps. Having one amp power all speakers may be asking too much, but will depend on how it's wired.
We have used these Onkyo amps before and they work great.
Onkyo M-282 - Premium Two-Channel Amplifier | Model Information | Onkyo USA Home Theater Products
