I have a Furman Elite 15 pfi which replaced an Adcom 515 for my source components. My amp is plugged straight into the wall. In my system {all tube} the Furman sounds much better than the Adcom. Also the two cord deal on the Adcom is a bit of a pain. I have never tried the Monster Conditioners. If I were to upgrade it would probably be to a Furman Reference 15i or 20i.
One thing about the Adcom, I have owned it for about 20 years now and the damn thing still works. I have never had any problem with it at all.