I have a B7610 with a 60" MMM and blower. I purchased the blower with picking up leaves as it's main job. (don't really care about the grass clippings in summer) It was NOT cheap, but it works great! Like previously stated, the only times that it works just ok, is on wet wet leaves. Though I have never had it clog, I just had to go over the leaves a few times. When dry, I can rake the leaves into a long row, then suck 'em up. No problem. It also shreds the heck out of them so that the bags fill up much mmore slowly than I would have thought. It even sucks up & shreds the Catalpa leaves. (they're huge)
I think the BX blower is a little different. The blower is in the rear and runs off he rear PTO (I think). Where as the B runs off the spindle of the mower and mounts to the side of the mowing deck. Anyway, as I said, it wasn't cheap, but if you hate to rake, or have lots to rake, this fits the bill.