There is a whole thread dedicated to this...as I was just looking up the same info a few days ago. Anyway I ended up purchasing 5MM for the front and 10MM for the rear. I was able to find a few pictures with this set up and I liked it compared to the 5/15 , 10/15 or the 5/15...I thought that the 15 in the rear stuck out to far. But that is just MHO.
I went with the H&R spacers. I'll give you a secret. You can go to ECS Tuning (
www.ecstuning.com) and type in the part number in the search area they have up top and it will bring up the H&R spacers you want. Anyway I got the 5mm and 10mm for 123 shipped. Only downfall I gotta wait bout 3 weeks for them to get here... but it was well worth the money I saved...plus the weather still sucks outside anyway.
I know that ECS Tuning only deals audi/vw/merz/bmw/etc but its thte same brand/part number that'd you get from IPD or anywhere else.
Example
http://www.ecstuning.com/Search/3035650/ those are the 15MM spacers if you wanted to purchase them... Notice the part number 3035650
You can go to H&R's website and cross reference it if you so choose to and don't believe me.
Hope that helps and good luck with your decision.