Hafler DH 500 update?

Well Elizabeth, I consider my purchase of the DH500 as one of my two worst decisions in my 35 years of audio (the other being the Adcom GFA-1 that couldn't drive anything but a 8 ohm speaker and would overheat and constantly shut down driving my DQ10s :( ). The 500 was a step down sonically from the 200. Perhaps they cut corners when it came to the power supply and upgrading that might improve the sound of the DH500. I kinda doubt it though.

"Tube in contrast seem to retain there dynamics at a lower volume level..Does anyone else feel the same?"

I do, and the lower I go, the more "single ended" seems to be the best. There are exceptions of course. I was surprised at how good my ss Pass XA.5's sound a low volumes. I read Nelsons description of the circuit and guess what? He biases these to run "single ended" at very low volumes. Even at louder volumes, you have times where the music decays into silence.

I think it is a tough call;would you consider using it for subwoofer work or surrround processing if you have that as a option?
Since you mentioned that is has not been used for many years I would have it looked over especially the power supply filter caps if they are still the original.