Hi All - I know this is an old thread, but I thought I would chime in since I have a D500... as suspected, this amp IS a beast. The one I procured was not working and I paid 1k for it. But it was from a buddy I knew and he knew the history of the amp. It was a little rough, and apparently well used, but still has a lot of life left in her.
The bottom end on this amp is unbelievable. Solid is an understatement. It shares the PL400 / 700II op-amp style PCB, but I don't mind that. This amp was not made for "boutique listening", it was made for recreating Saturn V rocket launches in your living room.
I'll take the covers off soon and snap a bunch of pix for the forum members here for a "virtual tour" of a D500 if you want.