Look again - they're not S4 wheels, nor are they S3 or S-anything. They are genuine Audi ones though, TT wheels actually, with 215/40 ZR 17 Goodyear Eagle F1 tyres.
From initial driving impressions, the ride quality is vastly improved over the standard Sport setup and there appears to be no rubbing issues as yet. I will be removing all 4 wheels again shortly to inspect the arches for any signs of rubbing.