If i was to change the S3 I would have no idea what to go for... the size for me is perfect so anything bigger doesn't make sense to me. RS3 yes of course but don't think I'll ever justify the cost and running costs, if I didn't do 10k+ miles a year then maybe... but still probably no
I like the 3 series BMW but again the size, 1/2 series..meh
Golf, well maybe.. I had a GTD for a day before I bought my A3 but didn't like the ride comfort, wasn't too keen on the interior either. Though it has probably changed anyway since then.
Mercs.. nah ..
Fords .. not a fan of the interior, looks too cheap / chavvy generally for my taste.