change of car!!!

hey all, i have a 53reg a4 190bhp quattro sport (b6) and its been remapped by revo and is loads better than standard and realy does go well but i am used to diesels and missing the low down grunt and most of all the fuel economy!! at the mo i get around 30-35 mpg, i love the car, its never let me down and never got stuck in the snow or ice and the spec is great but i am thinking its time to go for the oil burner again! i am looking at the 55-57 reg a4 diesel in either 140 or 170bhp. have you guys got any info or recommendations on these cars? mine has leather, sport pack,19'' rs6's, s-line pack, quattro etc and is totally mint so i would like a decent spec. i will miss it but fuel is the issue so what do i get?
is anyone after my car either to buy or px? anyone know of a diesel for me?

Thanks s3, yeh I have seen a few go for 7k+ I have looked at your seat in a garage and a very good way to go to get a to spec car but out of my price range! So do you think I should go for the 170? My mate has a 140 and I will have s ride out this week and see how it goes!! What mpg do you get?