I know someone at one of the largest car audio dealers in the US that sell all of the top brands including MB Quart, Kicker, JL Audio, Infinity, etc. and he told me that the Crystal 6 1/2 sounds as good as the MB Quart Premium Series which is at the top end. He also mentioned that this Crystal 6 1/2 handles the lows as well as an 8 inch woofer.
I have yet to hear it myself, but this guy knows what he is talking about. They have a display with the Crystal 6 1/2 component in their store to demonstrate what this speaker can do.
I want to get a pair to try out this year.
MB Quart has the reputation, but you pay extra for that. Crystal seems to be the high performing underdog.