igglebert:The A6 sound _slightly_ more forward and have a faster, tighter bass than the S6e. I've read in more than one place that the S5e was actually a better speaker than the S6e. The A5 versus the A6, however, seem to be a little more apples and oranges.
Intriguingly I read the opposite when I was searching!
I think it was David from Frankharvey said that the biggest difference (read improvement) is S5e -> A5, whereas the S6e ->A6 is less of a jump. Personally I prefer the S6e over the A5, but it wasnt entirely fair - the A5 was demoed with a Cyrus 8XP and the S6es with my K2. From extrapolation (dangerous I know) To my ears the A5s are a bit faster and leaner, a bit more 'demo room impressive' but don't have that fabulous organic midrange and overall neutrality that the 6s posess.
However, if you factor in price, then its a no brainer IMO, but it cant last forever....they did have some at sevenoaks for £1199 which was a steal.
EDIT - Hifix have some in Maple at £1500 or so, nothing on the 'bay at the moment. There is a relevant thread on this same topic on the pink fishy forums if you google 'Spendor S6e speakers'