With the rumors of a replacement for the MC501s, I have been trying to decide if I would upgrade. After, a day of listening,that answer is it is very unlikely. The thing that I do not like about Mcintosh amps is that you can not turn off the illumination for the letters that say Mcintosh. With my amps being placed right by the speakers, it is distracting as I do front projection. If I could completely shut off all illumination, that might actually make me upgrade. I know it is a small thing but it annoys me to no end that I can not have a completely dark theater without putting tape over the Mcintosh lettering.