Surprised to see power conditioners being discussed! My 20-year-old Monster HTS-3500 mark-iii is still going strong, but the power-delay relay for the 12v trigger is now starting to take a few clicks before it powers on the amp (I use it for a trigger to turn on an amplifier that has a proprietary 5v trigger), so I decided to replace it.
After some research, Furman seemed to be the way to go (non-sacrificial, doesn't restrain the amp like sacrificial conditioners can), so I bought a used Furman Elite 15 DMi used a days ago. I've unpacked it, but haven't had time to replace the Monster yet. The old Monster conditioners are pretty well made, but Furman is reportedly a superior design. Panamax actually bought Furman many years ago, but the products remain different in design I think (I think Panamax are sacraficial like the Monster).