Your surround speakers are supportive, not primary like the left, center, and right speakers. I have a very high-end theater installation, but, after a lot of investigation, I ended up purchasing Arendal 1723 THX speakers as my surround speakers. They have proven to be excellent. For me, their job has been to reproduce -- with high accuracy -- what they are sent by my preamp/processor; their bass capabilities below 80 Hz are not that important. A pair will cost you $1,849, and financing is available.
Good luck!