Zate,
Here's a link to the subframe debate over at corner-carvers.com.
http://corner-carvers.com/forums/showthread.php?threadid=4200
It gets a little off topic after the first page (berating the guy for essentially not searching and reading before he started asking questions). There's probably a better thread I could refer you to, but i'm too lazy to go look for one. Search and you shall find what you want. Really knowledgable people over there... but beware the newbie...
The bottom line... stay away from Kennybrown. Griggs is an excellent choice. MM is a VERY close second and definitely more economical.
If you're gonna be out at the autox this weekend, you can take a look at my MM Full-length subs.