From my time behind the wheel of one of those on a couple of long road trips I'd say the sound is spot on at medium to high revs, a bit too rough and bassy on the lower end. Even with a sport exhaust you basically only get that typical Audi/VW 4 cylinder turbo sound below 3.500rpm. I'd say it should be much flatter and overall it's about at least 50% too loud. The cabin in the old TT is super refined and there's tons of sound insulation, it is much more subdued from what I can remember.
Thanks for the throwback by the way! I hated the heavy steering (which I do on all Audis, never return to neutral on their own) but it was fun when driving it hard and the looks inside and out were something else, especially the tank sills they dared call windows . You absolutely nailed the cabin design/proportions!!