2.0T or 3.2? I know you can tow with them but i don't know if i would go overboard. Like a lightly packed uhaul trailer or bike trailer maybe. If you have a 2.0T I would suggest getting a chip for it (goapr.com) and that will give you a lot of extra power.
Check your owner's manual. Clear instructions on the hitch and on the weight that can be towed are printed in the manual. For most A4 models the weight limit for a trailer with no brakes is 740-750 KG, which is roughly 1600 pounds.
Search Audi A4 Avant Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Audi A4 Avant Experts