KEF LS50 - hands down (although they are they are technically stand mounts, not bookshelf).
I have had quality speakers before in a similar room to yours (Klipsch, Polk), with a Peachtree Nova at the time, but the KEF's represented a MAJOR step up. The soundstage and transparency are unmatched at this price range. Their Single Apparent Source technology is real, not just some marketing gimmick.