Wow, nice wheels. Typically these are very expensive but look the dogs. Difficult to tell if they are a good price or not without seeing the condition to be honest but they do generally fetch a premium.
Offset range needs to be between ET38 and ET52 (+/-) 7mm to go on withouts upsetting things too much.
Will you be keeping the tyres? What condition are they and do the sizes fit without buggering the speedo readings. Always be careful with 2nd hand tyres.
Finally check the spigot sizes. 57.1mm is standard Audi size. If the wheel spigot is too small then you will have to find someplace to machine the centres out. Oversized and you will need some spigot rings.
Personally I would go 15 rather than 16 but we all know that by now. And remember there a re plenty of borbet A's out there so don't be rushed. If you're not sure or convinced walk away
Your money is hard earned and easily spent, thats my motto!