Folks, I am planning on adding surround backs to my system (M-60, VP150, QS8 and Paradigm ultracube12), but do not have the funds to go with QS8s. I am thinking I can go with smaller speakers no problem without a huge difference in sound level and quality (afterall how much content comes from the surround back speakers anyway). What are people's thoughts and recommendations.

Thanks
p.s. I am driving everything with a Yamaha RV-V863.

M60s, QS8s, VP150 and paradigm Ultracube-12
Samsung BDP-3600, Nintendo Wii