I agree with Marty. I bought a set of BP10s in '95, and I should have never let them go. They are not the best speakers I've ever heard, but they are uniquely wonderful, and they're easily the best Definitive ever made. (I'm talking about the BP10, with the soft dome tweeter. That was a sweet, detailed tweeter. The AL one was awful. Awful.)
For some years I sold Definitive, right alongside Polk and Paradigm, and other stuff priced in the high 5 figures. IMHO, when DT started using AL tweeters, metal grilles, and subwoofers EVERYWHERE, they stopped making anything good. Perhaps things have changed since 2001, IDK.
The thing with bipolar speakers is, it's all about placement. I spent hours, and days, tweaking the placement of these (as I do with any speaker), and when you get them where they belong, man you'll know it. These things have good bass going WAY down - probably not to 20, but they're powerful way below where a couple 6.5" cones have any right to be. I never missed having a sub when I had these. It is true that a powered sub takes a big load off your amp. But consider that when I first bought the BP10s, I was running an entry level JVC receiver (rated at 80wpc), and it could make 'em LOUD with ease. Those things are easier to drive than . . . ahh. . . I got nothin'. . . your father's Oldsmobile, maybe. The point is, they are very sensitive and efficient. Just keep tweaking the placement until they sing to you.
The thing with subs is, it's all about placement. And, not surprisingly, the best place for your sub usually will not be the best place for your mains. Finding the ideal spot for a sub is so complex that, for most of us, the only way to do it is through the application of a few rules of thumb, and then LOTS of mundane experimentation. I'm talking, get a 25' patch cord, put on a Garrison Kiellor cd, then slowly crawl around the room, listening. Then, move the sub just a little, or turn it 90*, or move it 15' that way. And crawl around the room again. What I'm saying is, your sub probably does not belong where your mains are. And even if it did, do you really want all that reverberation physically connected to your other drivers? A good sub makes the whole house shake. No cabinet can honestly isolate that from drivers mounted 2' away.
Kini does make a good point about the newer speakers being easier to match to a center. But you can find a way to do it. You could buy a Porsche, and drive it without a hood ornament until you find one. Or you could buy a LeCar, because you already know where to get those stylin' door stickers. Your choice. (Of course, the choice really is yours. I merely offer my gentle opinion.) :)