Yamaha Aventage RX-A1020 Needs some speakers

Stay away from Adcom

http://app.audiogon.com/listings/solid-state-hafler-p3000-power-amp-2013-04-04-amplifiers-19403

http://app.audiogon.com/listings/solid-state-parasound-2125-great-condition-x-4-2013-04-14-amplifiers-75165-waxahachie-tx

http://app.audiogon.com/listings/solid-state-bryston-3b-amp-2013-03-25-amplifiers-17356

http://app.audiogon.com/listings/solid-state-acurus-200-x-3-modified-3-channel-200-watt-ch-amp-2013-04-05-amplifiers-27262-high-point-nc

You probably don't even need 200 wpc but since we don't know how big your room is, we'll start here and work our way down.

Since you originally mentioned three channel amps, I will limit the discussion here. Some 3 channel amps to consider are:
Parasound A31, 250 wpc, $3000
Anthem MCA-30, 180 wpc, $2100
Odyssey Stratos HT-3, 150 wpc, $1550
Emotiva XPA-3, 200 wpc, $700

Any of the above will more than get the job done with your CM9's. Its just a matter of how much or how little you want to spend and the level of quality you want. Finally, with a 3 channel amp handling the critical front three speakers, this will leave your Yamaha RX1020 to act as the preamp/processor and also power your surrounds for HT usage. The Yamaha will be more than up to the task just handling surround information. Hope this helps - happy listening!

Room size is 18'x 26' with 14' vaulted ceilings, lots of glass front and back, wood floors and half of one long side wall opens to kitchen.

What will be your mix of home theater/music? If your top priority is two channel music quality, you might want to consider a used McCormack power amp, possibly a DNA 1. Rated at 150wpc into 8ohms, but delivers a lot of current. I believe is also good down to 2 ohms.

This one would be really sweet, but is modified and may be more than you want to spend:

http://app.audiogon.com/listings/solid-state-mccormack-dna-1-deluxe-smc-gold-revision-2013-04-22-amplifiers-27617-raleigh-nc

Should you want more power for the center channel, you could always pick up an amp for that.

Thats a big room Bill. With a lot of highly reflective surfaces too.

If it was me, I would get the Parasound A31 at 250 wpc to drive the CM9's and Center. 3K and your done. Comes in Silver or Black. Keep your Yamaha RX1020 as your processor and also use it to drive the surrounds.

Then consider some room treatments or your going to have one very bright sounding system. And the amplifier you choose won't have anything to do with it. Good luck.