I'd have it Lowered & Spaced, Then Exhaust then Wheels
I agree with DBS - and that's the route most of S5 and many 3.0TDI owners have taken - at least we less well-heeled Brits and Euros!
Speaking of the S5, I think that essentially, the stock wheel is one of the better OEM offerings and whilst cars certainly look good running on 20s, there's no way the standard car looks 'under-wheeled' and the design is very well integrated with the cars looks.
If you're more preformance-orientated and want to save weight, that might move wheel replacement higher-up your priority list but it seems most owners set about addressing the preceived 'softness' of the production S5, freeing-up the sound of that V8 and attending to the stance through spacers/suspension mods.
I'm in two minds about wheels and having lived with the stock items for a year, currently at a crossroads - if I haven't seen fit to do it by now, do I really need/want to?
