You will struggle to beat the ED30 , having had one for 3 years i had £20-£25k to spend on a replacement and could not see anything that was a truly better , rather than just being newer . Fortunately i had a change of circumstances ... I retired and needed a "Tow" Car so bought a Freelander 2 !
As you say the engine is the same in S3 and R so you are already looking at it how i did , thought about an RS3 but they are a bit , just like an spiced up S3 , the engine was the only plus , but you can't use what you've got now can you ?
Only car i would trade an ED30 for would be a 7R , but thats £30k , but there's one on the R forum for sale .