I have an A6 2.8 Quattro 2001 model
I want to buy a nice exhaust that has a nice sound to it. What should I get?

 

"Nice" is subjective - what you like may be what I hate so my suggestions would not necessarily be good. Search YouTube for videos of your car with different exhausts - search for "exhaust" or "aftermarket exhaust" or the names of manufacturers and see what tones you like.

 

It depends whether you want a really loud exhaust or not. Budget is factor also.