Best Used Speaker Under $4,000 w/ Respectable Lows


I was once a member of the audiophile community (Some of the older Audiogon members may remember me) but had to step out for a bit do to life changes. I am thinking about stepping back into it in a limited fashion with the system configuration listed below. I would love opinions on what used, $4000 or less, speaker would best suit the following system. Note that I would prefer NOT to bi-wire and would love something with a respectable low end (A full range speaker would be nice). I tend to treasure transparency, neutrality, high end extension, speed, DYNAMICS, and tight driver control / integration in my speakers and leave bloom/coloring/musicality to the amp. I also prefer speakers that play very well at low volumes with medium power amps. Thanks for the help!

Transport: PC with Windows 7 / WAV Files / Foobar / Lynx AES16 PCI digital I/O card

Dac & Preamp: Berkeley Audio Design Alpha DAC

Interconnects & Speaker Cable: Nordost SPM

Amp: Sim Audio Moon W 5.3
drhst20
If you stretch your budget just a bit (~$4500 used) you could get a pair of Vandersteen Quattros. These speakers have internally-adjustable subs (with amps) that will provide full-range low-end. The rest of the speaker is also excellent. One other thing about this speaker that violates your criteria - Vandersteen recommends biwiring. I think you'll find the trade-offs very worthwhile.
Legacy Focus 20/20 or Coincident Total Eclipse (used). Both are full range, dynamic and fun. The Coincidents are a bit more accurate but the Focus are amazing in regards to slam and dynamics....both are within this price range on the used market.
Zu Essence at their new price is in your range. Read this monts Stereophile report on them.