PLC advice on API vs Richard Gray vs VansEvers?

Hi,

I'm in desperate need of purchasing a Power Line Conditioner. The Unusual Suspects are Vansevers Ref 850, Richard Gray 400 mkII, & some of the API units.

I would like to hear from others who have used Vans & Grays units. As these are the 2 I'm really shooting towards.

Or can the 2 be used together, as the Gray 400 unit really do not qualify as a true PLC???

And what is a Sub Station that Richard Gray makes???

Thanks in advance.