I find one works well and is worth the $110. Two is even better if you have a high resolution system. Really quiets the background noise in the system. Adds clarity and dynamics. You would want to experiment with plugging it either in a open wall plug, or into an open plug on your conditioner or power strip. If you try two, then do both. If plugged into the wall it will also assist other oulets on the same circuit. The change is more noticeable to me plug into a power center nearer the components.
I also own one of the original version. Don't notice any difference between the two. The Mk11 filters a wider bandwith. You can read a professional review of the Mk1 version at:
www.planethifi.com/planethifi17/mar01bc86.htm