The key is matching the front 3. The surrounds are less critical, in particular if not listening to a lot of multichannel music. Ideally, you do want your speakers (not necessarily sub) to all match and be basically from the same "family". IMO, the Monitors blended well with the former Performance series fairly well, but the Studios do outclass the Monitors by a fair amount more and they don't quite have the same timbre. I upgraded my speakers so that they would all match (5 of the same speaker), and it made a big difference with music - for movies, there was an improvement, but not quite as noticeable as with music (DVD-A, SACD) where the surrounds can be a much larger part of the experience.