What suspension kit is the best?
 

I have a 2000 A6 Avant with now 115000 miles on it. The front suspension was replaced around the 93000 mile mark and is in need of replacement again. I don't know exactly what kit the previous owner bought and had put on, but I would think it should have lasted longer than this. I have been shopping around and have seen all types of kits from Ebay, BLAU, etc...
Does anyone have any suggestions on which ones are good at a decent price? I am on a budget, so anything under $600 would be what I could afford. I have to save the extra $150 for my Audi mechanic to install them for me.
So, please help, the knocking noise is driving me crazy!