Hmmmmmmmmm, lots of helpful advise on here, but oddly, none of it actually answering the original question
It's an A3, so will have an 'overshaft' front bar, and no rear bar at all.
Beyond about 40mm drop, the front right hand drive shaft will start to catch the ARB in certain situations.
Longer drop links were once said to be the cure for this, but in reality, they don't work, as they throw the bar back, so the drop link itself catches the shaft instead of the bar.
Shorter drop links will be a slight cure within a very narrow range of ride heights, but if you go much past 50mm, then shortening the drop links will just end up with the shaft on the bar again.
In terms of ride height and suggested drop, you can drop an A3 a good 50mm before you start to **** things up hugely. They will of course ride better at around 30mm as suggested by PT, but down to about 50mm it'll still handle just fine and should ride OK as long as you don't have ultra bargain basement coilovers.
I dislike the suggestion that 'coilovers' lead to a poor ride. My track car on KW V3's rides better than any shock / spring combo I've experienced, and it's literally WORLDS apart from the nasty crashy **** you get from cheap ebay coilovers. It's simply a case of getting what you pay for IMO.
My old Daily was down about 50-55mm, with an H&R front bar to stop rubbing issues. It looked great, and still drove pretty nicely.
Much lower than this and it really starts to **** up the geo though.