I've got the 6500s running off an oldschool Soundstream D200II, and the combo is producing the best sq, best staging, best imaging I've ever experienced. I've been in and around the industry since 1988, and have dealt with numerous brands of comps, including MB quart, Alpine, Fosgate, Polk Audio, Soundstream, Focal, A/D/S, etc. The only thing I've heard that comes remotely close is my friend's CDT CL61A comps, which are close, but the tweeters are not remotely in the same ballpark, and their midbass isn't quite as good either.
If you can afford it, I'd recommend the 6500s as they are a HUGE step up in SQ over the 6000s. The 6000s are closer in SQ to the CDT CL 61s with the silk dome tweet.