A few things:
1) I have one from ebay (not one of the ones you show) and I noticed a difference when going over the railroad tracks near my house. Can't say what else it may have helped, as I am not the most in-tune driver.
2) Don't forget to figure in the inflated shipping costs.
3) They are adjustable.
4) I will have one coming off my car when I install my SC. I may sell it, or it may become a door prize at the SC install.