I've no experience with BL 3 or 11, but can chime in a little regarding the Quad. A quarter of a century ago my father acquired the Quad 66 series CD transport and amp and set it up in conjunction with BeoVox Pentas. The sound quality and build quality was second-to-none, and the best endorsement one can give is that he's still using the same CD transport and amp in his main system today. Played almost every single day, nothing had needed replacement or fixing in 25 years.
In 2001 I purchased the then brand-new Quad 99 series, with the smaller of the two stereo amps, and hooked it up to a pair of BeoVox CX-100's. It sounded beautiful, but almost immediately I noticed the large drop in build quality compared to the 66 series. Sure, the aluminium casings were weighty and solid, but the LCD displays and remote control looked ridiculously cheap, and the facade buttons had a poor tactile feel and responsiveness. The preamp unit failed within a year. The remote also needed replacing once. It's now set up in a secondary room with the Pentas, and for a while continued to produce beautiful sound, but a few years ago the amp started to make a very loud "pop" noise on startup and shutdown. Very recently, a faint distortion or "white noise" has started to appear on some recordings, particularly during high frequency parts. My car CD player exhibited the same symptom and the repairer attributed it to the laser being worn.
With that being said, my Quad 99 CD transport was of the first series. Your model, the CDP, is the second and may have had these issues ironed out. Or not. One thing I've learnt from this experience though, is that the adage "they don't make things like they used to" clearly holds. As the forum plainly shows, B&O is also suffering significantly from this malaise. High-end brands are sadly not exempt from the trend.
Leo
BV 10-40, BV 8-32, BL 9, BL 4, CX100, BS Ouverture, BS 2000, BG 4500, Passive, LC 1, A 9