The new A8 4.2 FSI quattro models are also now available to order in standard and long wheel base forms at £58,305 OTR and £61,685 OTR.
Deliveries of all models will start in July.
The new 348bhp 4.2-litre FSI engine replaces the 4.2-litre, 333bhp unit that has powered A6 and A8 models since launch.
It enables the A6 4.2 FSI quattro models to accelerate from 0-62mph in 5.9 seconds; A8 4.2 FSI quattros do 0-62mph in 6.1 seconds. All versions reach a governed top speed of 155mph.