I had 2 RGPC 400s's.
I tried hooking them up to my system all digital in one, all analog in the other, and then all audio vs all video (as best I could divide my components up those ways, anyways). Personally, I didn't see or hear squat for any kind of improvement. And then I talked to one of my EE friends, and he said the only way an inductor can influence the signal, is if it's wired in series. The RGPCs are in parallel.
I then got a balanced power unit (I have Equitech, but there's also Furman, BPT, Monster 7000, the Panamax 5510, etc), and *then* I got improvement. (Primarily a lower noise floor, and a cleaner video signal.) But if you don't have "dirty" AC to begin with, no power conditioner in the world is going to do anything.
The Exactpower boxes are also kind of interesting.
Lots of reviews at Secrets. But just like anything, your system is entirely different from mine, which necessitates the common disclaimer: YMMV.
[This message has been edited by Kevin C Brown (edited July 01, 2004).]