hi ed,
go to vmps' www & check out their subwoofer info. i have a pair of their larger subs, & am wery impressed w/the tight, textured deep bass these tings are capable of - especially at the price.
i also use the deluxe wersion of the marchand xm-9 - highly recommended. wery flexible - i'd be surprised if ewe couldn't match quality subs to the cls' w/these.
regards, doug