The Ultimate Audi, in my opinion, should be a sensible, understated, and mechanically awesome car. One that suprises with just how fast and composed it is. The TT-RS is a sports coupe, it should have exactly what it does have. What we are going for in this arena is excess; Not wretched excess, no, but thoughtful excess. Excess that hides itself, a gentleman's indulgence. So, the S3 is pretty excellent (Perhaps not the pinnacle, but I wouldn't know), but the RS3, the 5-door hatchback with 380hp and the utter assurance that it won't misstep, will definitely be the Ultimate Audi.
It might just have been easier to delay my reply until it gets produced
I agree with that and the cars Grand Prix posted. Everything else can pretty much go away as far as I'm concerned. Except maybe the old Quattro. And perhaps this:
Personally I'm waiting for the TT-RS with the epic return of 5-cylinders, but my personal pick is this:
The A2. Expensive when new, but now proven just to be miles ahead of it's time. Everyone now is striving for better economy and using all sorts of fancy technology to do so. Audi did it the simple way, ten years ago now - light weight (through an aluminium body), great aerodynamics (same Cd as an original Honda Insight) and good engines - simple petrols and turbodiesels.
The light weight gave it pretty good performance from reasonably low powered engines (under 11 seconds from a 1.4, 3-cyl turbodiesel, 1.5 seconds quicker than the tiny VW Lupo with an identical engine despite the extra size), and the shape gave it loads of space inside. Numerous magazines declared it one of the best driving Audis too, not suffering from the understeer and vague steering in most of their models, even the contemporary RS4 and RS6.