Decision made & the TT will be going up for sale early in the new year. I've gone from pillar to post and after looking into a lot of different options I've eventually come back to the one I started with - a B6 S4.
I was sold on an E46 M3 but after reading a lot of horror stories about expoding rear diffs and massive service costs I decided that wasn't for me. I was also leaning towards a 350z but I know I could live with the lack of space (half the reason I'm changing from the TT) - lovely car though so it was a hard decision.
One of the considerations I had was the cost of tax on a big capacity engine so what finally crystalised things was when I fished around for insurance quotes - currently paying 1100 euro fully comp on the TT and when I was quoted only 660 euro fully comp with 500 euro excess on an S4 Avant the decision was made.... I could live with the tax if the insurance is that much cheaper.
Now the big decision is Avant or Saloon......