I'm going to guess that 75% of the people on this forum who jump on the Bash Peavey speaker band wagon, never have even played through a Peavey speaker loaded cab.
Not saying thier speakers are any good, just that most products considered good or bad by a few on this forum are simply being echo'd by the rest based only on reading the others comments.
I own a JSX, I've had a XXX, my next amp will be a 6505+ and I'm a diehard Peavey fan. I've tried the 5150 cabs, and the XXX cabs and they left MUCH to be desired. Not to mention clips of these cabs don't really speak to their favor either. I haven't tried the JSX cab, and I'd like to if I can track one down, but going from owners who have had them, and hearing them..they ain't all that great. Peavey makes a lot of "diamond" gear. You gotta break some rock and do some polishing before the stuff really shines. I suppose the cabs go the same way. Construction wise they're fine, but the speakers aren't good. Swap them out and you have something, especially with the JSX cab and it's features.