It can be done but you have to be careful that in wiring the speakers, you dont lower the effective resistance below the amps rating. The 7700 is pretty heavy duty for this purpose but if you burn out a channel it will cost some $$$. You should ask Outlaw about the best way to do it. You can purchase a speaker switcher which will allow you to swap from one pair to the other or play them together. I think a company named HomeTech makes a device which s pretty reasonable ($100).

http://www.hometech.com/hts/products/audio/selectors/
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner