Don't wish to disagree but ca-canny as we say north of the border.
Yes the 1.8T is infinitely tweakable, but a decent 2.5 TDI V6 will run and run. 150bhp on tap, whenever you want it, a pleasure to own and that growl when you plant your right foot is addictive.
I owned a late plate 2001 V6 Quattro Avant Sport to 173k miles. Loved that car. Yes it's not cheap to maintain, but look after it and it won't let you down. Oil changes are key. Do it religiously every 10k miles and use quality Castrol Edge and a genuine or Mann filter. Needs the fuel filter done every 20k miles.
No major concerns. Timing belt, thermostat (genuine and tested) plus water pump every 80k miles. Suspension and brakes are a constant on-going job. If you're handy with spanners, then even better.
No issues with Quattro. Anything over 100k miles I'd be renewing rear diff oil for peace of mind.