AC Conditioners?

I bought one. A Monster HTS1000. My preamp buzzed when plugged into it. I got my money back and no more Monster for me. I found better results going to the hardware store, getting a six foot 3 wire 16 ga extension cord. Cut the jacket of of it and braid it. You can get new plugs for the end to plug it into the back of your amp. Believe it or not this helped enormously.

If you are looking for used stick with quality. Assuming you do not want to spend big big bucks I can recommend Chang Lightspeed or Vansevers. They are both built well to last. I have a Monster that does a good job with cleaning up my TV picture and video. Colors sharper. Not good enough for good audio.

I think it depends on how you define "functionality". It is my understanding that the filtering qualities of a "line conditioner" will remain indefinitely. I have been told, however, that the ability of the conditioiner to protect from power surges does diminish over time (which is also darn important) A garage manufacturer of such products informed me that the part (I can't remember the part name) that handles surge protection fails with age and that even computer type cheapy power strips utilize the same technology as is in most hifi conditioners. This reminds me....you can get surge protection insurance from you local power company(cheap) in case of disaster (because home insurance would not cover electrical surge damage).

I too have had good results with Chang Lightspeed. They have different models depending upon your system/needs ranging from quite affordable (the 3200) to somewhat more expensive (6400 or 9600 or 9900) but none considered high-priced. Changs are also nice because they don't constrict dynamics. The internal M.O.V. (metal oxide varistor) transient protection devices are good ones that don't degrade. Cheaper (low power rated) MOV's can deteriorate if they're hit enough times with large enough transients; however this is not usually an issue unless you take a direct lightening hit. Mike VansEvers has some nice stuff & it's tunable for your rig too. Have never tried them, but have read a lot of good things & Mike is a good guy to deal with (he worked with me on some other power issues). His recommendations regarding affordable way to fabricate a dedicated power line worked wonders for me! See this thread for details http://audiogo1.iserver.net/cgi-bin/forum5.pl?asund&963328979&read&3&4&Bob_bundus&53wNWQ6xyzUcg