The A6T4 is a step up from the basic A6 with faster and higher spec components across the board such as a Athlon 64 3400+ processor. The machine runs Virtual RPC-Adjust, and Windows XP, and STD are accepting orders for collection at the Wakefield show.
The A6T4 desktop machine doesn't come cheap at 1292.50UKP (inc VAT) with an extra 25UKP postage charge if you are not collecting at the show.
Links:
The A6
Press Release