I'm not sure that's entirely helpful.
The M5's sound, from the interior, is saturated with
intake noise - this is true of many cars, but BMW / M-division seem to really like a bit of intake noise (as do I, and it seems to be the thing that's puts the fire in the belly of many M-car proponents).
Now, I shan't go into too much detail, but because of the unique firing order of the S85 (among production automotive V10s), the intake sound is pretty unique, and is very lumpy. This forms quite the contrast with the exhaust note.
An R8 V10, by comparison, sounds like it's gargling hammers because the firing order is more "balanced" (in terms of pulse spacing) against the intake configuration, so the lumpiness doesn't fall out as easily.
Because both engines are uneven firing (common crank pins, 90° bank angles), you get pairs of cylinders on each crank pin firing at intervals of 90°-630° (instead of 72°-648°, as in the LFA or original 5.0 Gallardo). This is the same as most cross-plane V8s (although one pair is 270°-450° in that case). So, on the intake side, it
should sound like a US V8. A cursory glance at YouTube for all the cars I mentioned should be satisfactory, and you'd be doing well if you could distinguish between the intake note of the V10 R8 from that of the V8.
Gran Turismo has rarely (possibly only accidentally) ever included intake sound. PGR4 is the more realistic, in terms of interior sound. Unfortunately, its approach is probably infeasible for GT6.
EDIT:
M5 with unsilenced intakes - sounds a lot like a
V8.