I've seen a couple of pairs come up in the used areas on the Web. Keep an eye on:
1) pink fish media classifieds and trade listings
2) Hifi Choice magazine classifieds
3) Hifi World magazine classifieds
4) Other forum classifieds (think big tents
and Cyrus products)
5) Audio Emotion may have some listed in their
used kit page
6) 2nd Hand Hifi may also have some listed in
their pages
7) Moorgate Acoustics have a
used kit page
8) zero gain have a used listing
9)
Hifi Adverts is yet another site to watch
10)
Steve's Hifi also had a pair of S6 at some point too
11) Maybe call Rick at Musicraft and David at Frank Harvey Hifi to keep an eye out for you
There's loads of places out there but whether you get to audition, etc, is another matter. For what it's worth, there's some good deals on the A6 at Sevenoaks (Clearance).