To Falcon's point. I did make the changes in 2 stages, and listen to all 4 combinations, although not for more than a few hours each way.
To OBG, here are my thoughts:
The SDAs and the BP10s are two completely different animals. The sda's were great in a lot of ways, but on some media I didn't "love" the SDA affect (primarily HT applications). I also felt like for such a large speaker, they were a little light on bass. The bass that they did have was tight and very good (thanks in large part to the crossover mods that I did), and the very high notes were a little hard on the ears sometimes. I know that tweeter changes were available to help that problem on the SDAs.... sadly I never did try that.
As for the BP10s. They bring a LOT of bass to the table... but it's a little sloppy at times. I'm hoping that a crossover upgrade (planned for the future) will help that. The mids aren't as forward as the SDA's, and the highs are very warm (all most too laid back).
There are two big advantages to the BP10s over the SDA's. For one, the bipole speaker in my room gives a HUGE sweet spot. They sound good from just about any listening position, which is great because I can never sit still.
The second is that they're a little more exciting to listen to, especially for movies. For music I find them easier to turn the volume up. I listened to my SDA's low often because I couldn't stand the SL2000 tweeter's high end loud. Now the highs get lost a little behind the lows at low volumes though, which bothers me sometimes.
On the other-hand. The SDA's.... when sitting in the right spot in the room, listening to the right track at the right volume...... were magical to say the least. I haven't had that 'WOW' moment with the BP-10s yet.
As for the B&K vs the carver.... I like the B&K for a lot of reasons. It handles my HT needs and music needs in a single, remote controlled package. When set to direct it imparts very little of its own characteristic on the sound.... Letting my Jolida CD player do all of the work with all its tube goodness. It doesn't have the phono section of the Carver (or any phono section for that matter) but I'm going to fix that in a big way soon.
I don't miss the 'sonic holography' on the carver either. I found that to be great in near-field listening with my monitor 4 bookshelves, but not as good in the big room with the BP10s.... and definitely not with the SDAs.