Standard fit equipment seems to be on par with the V6 models so xenons, climate, heated seats on the 'regular' seat models and all the electric doo dahs etc
My mate's has the no cost option of regular sport seats as opposed to the Recaros that they came with, comfier for regular use but really lacking lateral support, recaro equipped one would be my choice
Comes with no back seats and a brace bar and luggage net instead, cruise is an easy retro fit and all will come with a CD player, nav was a funny one on the TT as none ever had a full screen nav, was single din with a control unit down by the handbrake iirc
Current S3 brakes wont fit as the TT is 5x100 PCD, Brembos off a Cupra R will though and super cheap now, remap sees approx 270