I had a k04 on my old Passat and was running hella more than 225? I thought it was only the early s3 8l that ran k04 and then they changed it to k03s because of efficiency?
For the price difference you can't go wrong with an S3. All the extra goodies it got is worth it. Not to mention the beautifull wheel arches.
IMO if you buy an A3 you will spend a lot making it look like an S3 lol, why bother while the price difference isn't huge.