There looks to be two different styles of subframe, not just in the transmission mountings, I paid £25 delivered for an A6 V6 subframe so it was easier to fit the V8, the top subframe is the original and the A6 V6 subframe is different on the front crossbar it is lower and gives more clearance for the sump. I have also seen this style listed as an A4 subframe.
Putting a level across the front mountings and measuring to the crossbar showed the difference in clearance
A6 V8 Subframe - 98mm
A4 1.8T (top in picture) - 86mm
A6 V6 (bottom in picture) - 105mm