There are several different size rotors all listed as for my car (2006 A4 2.0T quattro). They go everywhere from 288mm up to 345mm, but 321mm seems the most common. Do they all fit or is there some other way to tell which ones to get (without pulling the wheels)?

Any particular brand? ECS Tuning has a bunch of different ones anywhere from $70-200 for a pair. Local auto parts stores want about $200 (or a little more) per pair.

Any reason I shouldn't just get these and call it a day? Audi B7 A4 Quattro 2.0T > Braking > Rotors > Front > ES#2500629 Brake Rotors - Pair (321x30) - 8E0615301AD

 

Or there's this option from Amazon (ships with Prime): http://www.amazon.com/Wagner-BD12543...pe=5&carId=001

Ignore the picture, it's a rotor, but it's a 288mm according to the same product number on Advance Auto Parts' site: Buy Wagner Brake Rotor BD125433 at Advance Auto Parts

 

I tried. Cheapest in-town rotor I could find was $100 for the fronts. Each. I finally gave up wasting my time locally and ended up ordering some decent looking Meyle rotors from ECS Tuning for $114/pair shipped. I was going to just get the Akebono Euro pads from them too, but I found Place For Brakes had them for $85 with free shipping and couldn't pass that up!

All-told, $200 even for the parts.

For anyone looking, I talked to a guy at ECS and they said the 321 (sometimes labeled 320) mm rotors are standard for the front. The 288mm is rear.

OEM / Performance Parts for Audi, BMW, Mercedes Benz, Mini, Porsche & Volkswagen - ECS Tuning
Brake Pads, Brake Rotors - Best Deals on EBC, Brembo Kits and more | Place for Brakes