I really like herpstat products. There are perfect. One thing to keep in mind. Picture how much 3in, 4in, or 11in flexwatt it will take to make 550 watts. I use 550 watts per channel to be on the safe side. That unit will last you a good while unless you have one of those fancy "money tree's" planted in the back yard.. lol

assumption: used for racks and considering herpstat II model.