Sufentanil got it right. I currently have an all-Gallo Reference surround system - 3.1 Refs for Front L/R, Ref. AV Center for center (duh!), and Ref. AVs for the rears.
Prior to that, I was first using some Paradigm Atoms. They played, but were not a good match at all. Then I was using Gallo Dues for Center and surrounds. It sounded pretty good but the timbre-matching was not ideal. Finally, the system took a noticeable leap forward when I put the Ref. AVs in place of the Dues. They were significantly more expensive, but well-worth the investment.
The left-right and front-back transitions are now "seamless", there is no obvious "hand-off" from one speaker type to the others. This results in a much more enveloping soundfield and the sound quality is definitely improved.
I am now *quite* satisfied with my system's overall sound quality with the exception of my subwoofer. Once I get the funds, I will probably opt for a Velodyne Optimus or DD Series subwoofer or soething similar. Having a subwoofer with enough "coneage" (12" or 15" driver) and "grunt" (big power) and a built-in DSP and room correction technology is very important for the 16-60 Hz region.
Conversely, I may retire the sub and power the 2nd voice coils on my Ref. 3.1s using a sub-amp/crossover combo. The Ref. 3.1s are supposed to be able to dig down to 22Hz when doing this properly. I have heard this combo and it sounds very, very good.
Finally, it would be helpful if you could tell us what speakers you are currently using...