Did you have an luck with the noise isolation devices for the coax cables? My guess is you may have noise entering your system from more than one source?
I do not have experience with a UPS in an Audio System. Trouble is all these devices (surge protectors, power conditioners, uninterruptable power supplies, etc.) make claims yet I have found big differences in how effective they are.
I don't think a UPS necessarily provides better power conditioning. I go back to the Furman AC-215a that I purchased, I have been impressed with it's power conditioning capability. Furman has other products with more outlets you might want to consider.
This might be of interest: http://www.musicplayers.com/reviews/...rmanAC215a.php