I have the GTX-D rhodium for my wall outlet. I have tried the gold in a power conditioner and would only use it there.
There are places where you can find the frame and cover at a discount, but it's worth the full retail cost. I was hesitant to add the frame but there's no looking back after you do.
I only added the cover on a whim because I had store credit, but it does remove a level of haze (that you didn't know was there) by minimizing smearing. Overall it's a very nice step up in performance and there's no going back after you install it.
I have also tried the Acoustic Revive outlet frame, but it wasn't my cup of tea.