Believe it or not, and I am not saying this because it's about "my" system, but the surround backs in their current configuration not only sound great, but with the right content absolutely fool me into thinking I have more space back there. It was not like that out of the box though, I had to tinker with the channel levels quite a bit (SR -3.0 db, SBR -2.5 db, SBL -1.5 db, SL -1.0 db) to get them to blend evenly in my space. It really helps that they are above the seating position. In addition, the 3805 can be programmed to the tenth of a foot for distance from speaker to listener. Also, because they are bi-polar as well as being run full range, they are a LOT less directional than the smaller monitors I used to have. These all contribute to a more natural sounding surround image.
Some material that may help you in getting "balance" in your rear channels:
The Bourne Identity -- lots of thunder and lightning from the surround channels at the beginning of the movie. If your reciever allows it, great matrixing of the SB channel(s) too.
Ghost in the Shell 2: Innocence -- this is my reference DVD for surround back information. This movie, in literally every scene, has
something going on in the SB channels. The gunshots from directly behind you in the shootout scene are EXTREMELY impressive. Lots of "soft" stuff happening in the surround channels as well (footsteps, someone cocking the hammer on a gun directly behind you, too many examples to list). Get this DVD, you will thank me.
Mr. and Mrs. Smith -- this movie absolutely rocks, even if you don't like bradjolina; great mix with lots of stuff in the rear channels.
Casablanca -- just kidding, but get it anyway best movie of all time
Best of luck in your setup, post or pm me any time if you'd like to talk more specifics about your room/equipment.
Regards,
chux