I have a dilemma and I haven't had a chance to do a listening test as I don't have the BL4000s yet.  Currently I have 2 setups, one is with my surround setup using a BS1 and 4 BL6000s as surround speakers.  My center is a pair of BL3s (yes, a pair of them, and it sounds fine, discussed this in a separate thread).  I was using a pair of them as I got a great deal on them and that's what I had.  Since then, I have another setup using a BS9000 and a pair of BL3s in a stereo setup for TV and music in another room (large room).  

I was able to secure a deal on another BS9000 with 4 BL4000 speakers and got a great deal on it.  I plan to sell the second BS9000 and some of the speakers.  My question is given these two setups what speakers whould you keep?  The BL3s or the BL4000s?  The difference in cost of what I could sell the BS3 and BS4000 is probably $2000 per pair!  I'm not sure that I really need the BL3 for either setup!

I would keep the BL3...  great technology and tons of options on placement.

Keep the BL3.

Sound great, imho much clearer than the BL4000. 

Any ideas from folks who prefer the BL4000?

Having both speakers at home, I can only recommend BeoLab 3, like the others, they are more compact, lighter, have a lower power consumption, and except for the SPL which is superior on BeoLab 4000, there's no reason to go for them if you can have the 3s

I like 4000s - well integrated sound with plenty of bass from a small enclosure. Also will fit in visually without making too radical a statement. The BL3 is definitely clearer but this can be tiring to listen to for prolonged period and the sound does sometimes seem to be divided into the sharp top end and the rest. They also don't do loud volumes well regarding bass which can become ragged.

Having said all that, I would keep the 3s! They are the better all round speaker and as long as you don't really push them, they are great.