I don't know. They seem a bit redundant when you have shelf EQs.
I know a freeware one, in case you want to play with it without having to pull out your wallet:
TAL-USE (scroll down a bit):
http://tal-software.com/products/tal-effects
I've played with it a few times. It does what you'd expect it to do and that's about all I can say about it.