Auburn,
I've been using garlic supplements which have been standardized to contain a minimum of 4000mcg or more of allicin for about 6 or 7 years now. For the past year or so I've been using a Puritan's Pride garlic supplement called "Maximum Garlic 6500", which has a minimum allicin yield of 6500mcg. So far, it is the most potent one I have come across. Before that, I was using a standardized Vitamin Shoppe brand containing 6000mcg allicin. The Vitamin Shoppe brand is also available in a 4000mcg potency. Regardless of the brand, it is probably a good idea to select one which is standardized to contain a minimum of 4000mcg allicin. This is the allicin yield that the German studies were based on, and what is generally recommended.