Hi, Im new to the Audi, i have an a4 (2000) and on the head unit, it says concert... Am i right to say that this is the Concert I unit, not the Concert II??? I went to my audio shop, and they told me that i could use the existing head unit to power a pre amped sub, is this true? arent pre amped subs like normal subs? The guy also said that the standard rear speakers are amped... Is this also true??? Cheers, Dom