I demo'ed the DC6Ts, the RX6s and some RX8s in Sevenoaks Audio a little over a year ago.
With my amp/CD player, I felt the DC6Ts had a bit more punch at the lower end than the RX6s, but they had a bit of a different colour through the rest of the range. I wasn't sure which I preferred.
I then tried the RX8s and was utterly blown away - such a massive step-up. I was nearly weeping in the store. Suffice to say, I ended up with the RX8s. I finally tried whichever KEFs were price-equivalent to the RX8s, and they were excellent, but I was not as emotionally attached to them!
I guess the moral of this story is that it is probably worth demoing them if you can, ideally with your own equipment.