Having spent a number of years chasing the high-end 7.1 HT scenario, I definitely agree with all the feedback above; matching of LS, RS, LSB and RSB speakers is essential. If your surround-proc allows it, go for a subwoofer up front and one for your rear channels as well; you won't be sorry. Alternatively consider my last config involved ditching the smaller LS, RS, LSB and RSB speakers that I had and going with a pair of full-size, full-range speakers in the rear that matched my front channels. It was well worth it and frankly HT and multi-channel audio never sounded the same ever again....
how much did you spend on rear surround speakers?
I thought i would share my experience setting up my home theater speaker system. I had Dali Helicon MkII for my fronts and Dali Helicon center. my side surrounds were an old M&K from one of their early surround systems. I replaced the M&K side surrounds with Dali Helicon C200 and was very happy with the sound. I moved the M&Ks to a rear surround position for my 7.1 system. However, when i found a pair of Dali W200 on Audiogon i bought them. After setting up with Audessey from my Marantz AV8801 processor, i was extremely pleased with the improvement in sound. I was very hesitant to spend much on side and rear surrounds, but in my experience, the extra dollars to have matching voices from the Dali helicon line actuallly made a difference i could hear.