Shunyata Guardian 4-HT vs. Chang 6600 MkII vs. Aud

Shunyata Guardian 4-HT vs. Chang 6600 MkII vs. Audioprism Powerfoundation 3 vs. Richard Gray Power Company 400?
Anyone have experience with any of these?
I'm looking for protection/filter/conditioning for a dedicated line. Unfortunately, I have to use this single circuit for all equipment. With no protection I get a "pop" through my system with washer/fridge/dishwasher when they come on. With amp on dedicated circuit with a BC noise hound and everything else on another common circuit with a monster power surge protector I get a hum. All equipment on the single circuit eliminates this. I am using a Mondial magic box, so there is no ground loop from the cable. Also, should the dedicated circuit be raised from 15A to 20A if needed to power everything? Any info or advice would be appreciated.
my system runs off a single outlet that shares one circuit for most of the outlets in my 1920's condo and found significant improvement using a pair of Richard Gray 400's. I almost certainly would not have bought them based on their claims but after auditioning in a single and double configuration went with a pair. Everything is smoother, quieter, blacker, more focused, with no apparent tradeoffs. Definitely worth an audition.