Bryston 7BST or bridged 4BSTs

A while ago, a dealer told me that the bridged 4's would not produce the same quality level as the 7 since the 7's are not merely two 4's put together. I've owned the 3st, 4st and 7st and they do sound differently. The dealer had nothing to gain by telling me that and did provide me an explanation -- I just don't remember the details. Sdcampbell made a good suggestion to contact Bryston directly. There must be something there or Bryston would simply allow for the bridging and not bother with the 7's (I don't think Bryston is a marketing hype company). This is not the case with all manufacturers since the Sierra amps sound better (and are predominately designed for) running in the bridged mode.