Subwoofers with Fritz Carbon 7's?

I'm contemplating going from full-range speakers (Polk LSI15's) to the stand mount Fritz Carbon 7's. However, I'm concerned that I might be given up some of the bass I'm use to having. Is anyone using the Fritz Carbon 7's with a subwoofer. If so, which subwoofers, and how's the combination. I'm using Van alstine and Odyssey electronics.

Thanks,