Last week I was listening to the M80's using an Audio Trak professional (150 watt into 4 ohms x 6 channels) poweramplifier. Using the Realistic SPL meter, I was getting 102 dB average and peaks as high as 105dB with no clipping what so ever. In a room that is 4000 cubic feet. I was approaching concert volume levels. It was as clear as a bell. Now I don't normally listen at those levels as I value my hearing, but is was nice to know I can get there if I want to.
My point is, I don't think you can accruatly detemine how much power you require without an SPL meter. It is as important as a tape measure is to a carpenter.
Before you can decide weather to go separates or not, you need to determine how much power you require, or will require in the future. If you want to get to near concert volume levels (105dB or greater) in a 4000 cubic plus room, I don't think a AVR is going to get you there. However, if 90db is all you need, then a 100 watt AVR should be fine. Generally speaking.
