Only have heard the BL11 once and decided to buy the BL2 (combo with BL8002). Even for music the BL11 did not sasify me, but my wife always tells me I`m a little dyslexic regarding music (too much bass). If you like a deep punch, especially for audio and would like to keep the BL3, try a PV1 from B&W (also very B&O-stylish) or the BL2. If you only would like to give your BL3 the possibility to "breath" and add some deeper volume, the BL11 does a pretty good job. Lot`s of guys with a pair of BL3 are very satisfied with them. And I have to admid, they are very good looking and you have lots of colour options.
But, if you have enough place, the combo BL3 & BL11 is not in the same league.
BeoVision 8-40, ATV2, BeoSound 4, Front BeoLab 9, Rear Beolab 4000 MKII, Beo 4