My buddy is running a full RF-7 system(RF-7's, RC-7. RS-7's, RSW-15) in an 18W x 23L x 8H with an Onkyo TX-NR5009(same as the Integra 70.4) and believe me it is not lacking grunt. Very dynamic with action movies and never seems to break a sweat. Try the 70.4 and if it is not enough oooomph then just add an outboard stereo or 3 channel amp to the mix later on.
http://www.accessories4less.com/make-a-store/item/intdtr704/integra-dtr-70.4-thx-9.2-140-watt-networ...
Bill
http://www.accessories4less.com/make-a-store/item/intdtr704/integra-dtr-70.4-thx-9.2-140-watt-networ...
Bill