What used speaker would you buy with $20,000-$35,000 and why?


I'm closer to the 20,000 part, but if I get stretched i would like to know higher recommendations. Remember, this is on the used market - not retail. I'm even interested if you think I should make a huge jump (say to 50,000), but I want to know what justifies that jump. I'd like the best bang for the buck and even the worse bang for the buck. Are there speaker lines that are totally overlooked that sound wonderful in this price range that I need to be exposed to? I may go higher, but lets start there.

PS Let's just assume the upstream equipment is adequate to drive any recommended speaker. We are not limited by upstream components.
Ag insider logo xs@2xnab2
The room is crucial. Fortunately I have a really good room (once I resolve an issue with the floor joists - I have to run a beam in order to cut the span in half and stiffen the floor). So I really suppose the question then is independent of room - IOW's assuming an ideal room. I didn't know that about the Vandersteens.
NAB, I know of a dealer who has a similar problem with floor joints.  He put some steel plates under the speakers I believe.  The Vandersteen Quatro on up is the best speaker I've ever heard of in their price ranges for dealing with bass.  Richard has been doing this for soo long, that he just gets it.  There is a reason his speakers are some of the best selling high end speakers of all time.  I have many friends who own his speakers and are able to keep them p against the wall or even pull them way out to get an even better sound stage and they never worry about the bass.  Where do you live?
Nab, I remember a former post of yours saying you lived in Georgia.  HiFi Buys in Atlanta is a great Vandersteen dealer.  He has a lot of other choices too so you can see what YOU like and they are great helping with set up too.  Let us know what's up.
Thanks Ctsooner. I will go up there and take a look. I got two monoblocks from them awhile ago (sight and sound unseen and unheard) - of course I don't think I can afford new Vandersteens I'd want (i.e. Model VII - $62,000 list) and, if I can, I'd have to come up with some crazy story for my wife! 
Nab2, send me a message.  Let's talk off line.  Don't want to clutter the thread as I have a question or two.  Thanks.