Nobody ever compared the two units? That's hard to believe. Please don't be shy to chime in if you have.
I've owned both at the same time and I think that the S300 is faster than the Evo and brings out a bit more of the recording room cues. The highs are better delineated as well.
Now, the Evo II is warmer with a slightly fuller bass and mid-bass. I liked them both very much, it just came down to personal preference. I kept the S300, but I do miss the Evo though...
I have an Evo2i and recently auditioned an S300i and Pre3/A1000 setups.
The Pre3/A1000 was heard whilst on holiday in Singapore, and as it had a rather more reasonable price tag on it, was seriously considering.
The Pre3/A1000 has a very similar presentation to the S300i, but is simply better in every way.
I then heard the S300i vs my own Evo2i. My opinion is that the S300i was brilliant in "hi-fi" terms, yet somehow lost the plot from the point of view of involvement in the music. To quote a Linn user, the Evo was simply more toe tappingly fun. Can't explain why, but I couldn't get excited about the S300i.
So I'll be keeping the Evo2i, which is fine as it also saves me some dosh for an even better front end.