I've heard very good things about the roller bearing IHIs and by all accounts they do provide as close to the best of both worlds as you'll ever get from a 1.8(or 2.0)T engine.
Even if Jabbas rollers read a shade high compared to some, their cars will still be making a genuine 340+ BHp...which will make for a quick car.
I'd love to try a decent IHI just to compare...maybe one day.
Back to the original subject matter though:
I think I'd be looking to do some bottom end work not just fit a big turbo - which is the logical next step for most people anyway.
Better rods, bolts, lighter flywheel etc...to make a bottom end safe to 7500, if not a shade higher.
Then, 18" wheels, a big turbo, and a 7500+ reliable engine WILL give an achievable 0-60 in second S3.
I'd also dump the standard flywheel/clutch set up and go for a single piece flywheel and uprated clutch to make sure you can actually deploy the torque as quickly as required to hit 5.xx second 0-60s.