I used Monitor Audio B2 bookshelves as my rears for a while, but they where moved to another room to make room for vignettes when I had the chance to pick them up. Both are nice speakers, but there is something about the ATF in the ML surrounds that complements the big panels in front. Watch a few movies like the new round of "Star Wars" and listen for the starships that continually run from behind your head to the front of the screen. They sound the same the entire way through, an almost seamless pass off from one speaker to the next.
Just my $.02, the monitor audio speakers you are looking at would perform great as surrounds.