I recently added an Ultimate Outlet for my amps. I think I heard an improvement (which probably means I couldn't but I didn't want to admit it!). I purchased it as one of several AC mods including Quiet Lines, a Wattgate outlet and a Monster 1000 (for the front end). I felt the same about each on of these individually--little if any improvement. However, when I combined them all the synergy was incredible; perhaps a 20% improvement in the sound. I now firmly believe in AC tweaks but the process does seem to involve a lot of experimentation and Brownian motion. Good luck.
PS Audio's Ultimate Outlet
Anybody out there have personal experience with this baby? It sounds good on paper. I have their Juice Bar and am happy with it. Hooking up with their outlet seems like the most cost effective thing to do. At least that's what they say. Anyone out there have the first hand scoop?