New Quad owner here. I purchased the 21L's in limited edition Yew finish just this week. Have them in a dedicated 2-channel system connected to a Unison Research Unico integrated that received the Underwood Hi-Fi Level 2 modification. Using an Onix CD-2 with upgraded Burr-Brown OPA627 op amps and a Rega Apollo as source components. The sound is very detailed and IMO neutral. Still breaking in but very apparent that this speaker will identify weak links in the component chain. Bad CD's sound terrible and well-recorded ones sound amazing.
These 21L's are relatively small - barely 32-1/2" high with carpet spikes installed - yet they project a big speaker sound with much better vertical dispersion than I would have expected. The overall perception they create is one of great tonal balance and clarity without grain or harshness. Listening fatigue simply never enters the picture with these speakers in my setup. YMMV, of course.
The build quality of the speakers is first class, too. I know they are made in China, but the manufacturing and QC processes seem to be well implemented. The Yew finish is quite attractive, although I would have happily taken birdseye maple or rosewood if necessary.
IMHO, the Quad L series are one of the best-kept secrets out there as far as price-performance ratio. Not a lot of reviews on them, but what you can find on them is generally very positive. I have yet to hear a single bad comment with respect to the 12L and 21L models.