Ilcho, I have a DH-500 sitting right next to me, unused, if you are interested. I'd say it is cosmetically 7/10(being really critical), but in perfect working condition. I have used to it to drive a pair of subwoofers for ~4 years without any problems at all, but the last year I haven't had any use for it.
Shoot me an email through A'Gon if you are interested.