if i were you, aside from looking at AVR's with the # of channels you want, i would also look at how much power you need to reproduce cleanly the most demanding music/movie source you intend to use, and then double the power you will need (+3dB) just for headroom and caring for future needs. The front speakers along with the sub are the most demanding, power wise.

if you have a look at my room, you will see that it's quite small - around 1500 cu. ft. plus an open doorway to the kitchen = 3000 cu.ft. - and i sit about 6-7 ft from the front speakers.
when i play some demanding movie at Reference Level, the front speakers need around 300 Watts/ch.

if the AVR's power output is not sufficient for your needs, i would seriously consider either Emotiva amps or some pro amps from reputed makers, like Crown or Peavey or QSC or others; (QSC has a 6 year warranty).
those amps have the advantage of having sensitivity potentiometers, so it's much simpler to adjust levels between fronts and surrounds and the sub.

your Yamaha is 90 W/ch, but only when one channel is working; with all channels working at the same time, your effective power could be around 50 Watts/ch. Clearly not sufficient for some music and lots of movies at Reference Level.

Last edited by J. B.; 09/02/12 11:13 PM.