The 663 is rated at 400 watts for power consumption, and here's some measurements-
http://ultimateavmag.com/avreceivers/608yam663/index7.html
Now assuming it's true that a regular receiver cannot effectively output more watts than it consumes (read that somewhere a while ago, don't remember where now), I would assume it's safe to say the Pio 01, 03 and 1018 will probably not have anymore power than the 663 with their 390 watts consumption. Of course that is an assumption, and I have not seen any measurements on them yet. And if my assumptions are wrong hopefully someone will correct me.
From what I've heard from others, the SC-05 might give you the additional power you're looking for since it is using the ICE amps, hopefully some owners can chime in. It's not anymore power hungry than the other Pioneers, but I believe the ICE amps are a different beast than the amps in the other receivers and much more efficient. How they work I cannot explain off the top of my head without researching them again.
Also the Onkyo 876 seems it may have pretty good power for 5-7 channels. I couldn't find anything on that one yet, but assuming they did not skimp on the amp quality from the previous model there's some mesurements here for the 875-
http://www.soundandvisionmag.com/receivers/2463/test-bench-onkyo-tx-sr875-av-receiver.html
I have the Denon 3808 which has more than enough power for me and would probably work for you too, but since it wasn't on your list I cannot say how that would correspond to the 2808 you mentioned. Since the 2808 is being replaced by the 2809, you can probably get a great deal on it and I would think that would be a good value pick if it's anywhere near the 3808 in quality.
Those would be the top 3 I would try to find out more on from the ones you listed if it were me. When I got the 3808 I was limited on the height of the receiver, so the 876 and SC-05 were not even options for me.
Good luck with your decision, hopefully some more knowledgeable people will chime in this weekend.