Lol well that might be the only thing that they've demonstrated common sense on!
The old vette and camaro transmissions should be good up to 1000hp, at least the 6 speeds. Don't go by what GM rates them at on the website as they go well beyond that. I don't know about the A8 though with an certainty. Lots of guys have gotten up around the same power level and haven't had a problem, but there are always exceptions. I'd be more wary if it's an early built car.
Good lucky with it
. If you want to save a few bucks try the eForce. It should be identical in how it creates power and the other guys seem to like it. The Magnuson is probably over engineered, but you get what you pay for.
__________________
Ordered 3/8/16- NFG/Ceramic White, M6, MRC, NPP, 6 pots, blk blade, no sunroof, blk splitter, blk bow ties, dark tails, nav.
ARH 1 7/8" ceramic coated full sys w/NPP; Maggie 9.2psi (85mm); Jannetty rough idle cam(TSP), tune and LT4 fuel system; Forgeline VX1 Black PVD (20x10,11); R88R 315's; ALPriority; BMR rear arms, bushings, DS loop; RF intake (red); nGauge
93 octane: 712rwhp, 654rwtq / E85 (E66 mix): 734rwhp, 674rwtq (SuperFlow Dyno)