Have to admit, the S/RS was genius on Audi's part.
To everyone else, a 335 is 'just' a 3 series, while S4 is perceived as a ///M rival. Even on the forums, Ive read of people comparing S4 with the M3 (In some thread about track times). Hell, I don't blame them, even the S4 has 4 exhaust tips, while a 335i only has 2. (not saying more exhaust is necessarily good, but it gives it a higher perceived value)
The A5 is also a great example, while technically being a 3-series/c-class coupe competitor, the higher numerical value makes the impression of a higher-end car. Luckily BMW has realised this and is now naming it the 4-series instead.
I like how BMW has named the M135i, not quite an 1M, but still an "M" nonetheless, it would have been interesting if they named the 335i the M335i..