Kevin, I used to own a set of the B&W CM1 S1's and found them to be superb from top to bottom. What surprised me the most, was just how deep that they could play. Often found myself checking to make sure my sub what not on when listening to them. Not to mention, the quality/linearity of the bass was second to none. Never ever had a 5" mid that performed so well. Just love that laid-back, lushy, and rich sound that was quite warm in the mids with an extended top end that never was fatiguing.
The 600 Series uses the same exact drivers as the CM S2 series. The differences between the two are in the cabinets albeit finish and/or bracing AND the cross-over components employed. However, it has been very well established that B&W uses low order cross-over designs. The less is more approach if you will.
If you really like the 683 S2's I say go for it. I am not a tower guy myself, but each to his own. The 700 series is said to be a BIG step-up from the 600 Series. In fact, I would love to own a set of the 705 S2's. But, at $2500 a set they are certainly out of reach for me. The 706 S2's and/or the 707 S2's also look rather appealing to me. Best wishes.
Cheers,
Phil
