I would not bother with the 2.4 v6 but consider the 2.8 30v over that and what you will get is 195bhp of power and get a Quattro for a lot less than say the 1.8t Quattro.
The V6 as you know is a smooth engine and even more so in the 30v format with a major power difference over your old 12v 2.6 Audi so if you was happy with the fuel bills and you are not looking at performance mods then take the 2.8 30v over the 1.8t.
Now if you want to mod and want cheaper fuel bills then you will want the 1.8t and I highly recommend Quattro as a major plus on both engines. The 2001 1.8TQ comes with 180bhp (Euro Spec) as standard and can be mapped to 210bhp + so making it quicker than the 2.8 and still cheaper on fuel. The thing you loose with the 1.8T over the 2.8 is smoothness as you have to work the 1.8T engine hard to perform like the 2.8 does with very little effort plus do more service stops to keep the Turbo happy.
Anyway I hope that helps and my opinions s are based on the fact I have owned both and have a 1.8T as my day to day car now.
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