Hi Daveyf, your JRDG Model 8 vs 501 findings do not surprise me. JRDG 501 was a relatively early design using ICEpower, besides not being intended as a Model 8 follo-on. Have you tried Bel Canto Ref 1000 Mk.2? It is a more recent design perhaps, with a little more advanced power supply regulation. . . I suspect you may find those more musical than JRDG 501s.
As for other brands, I freely admit that my musical/sonic preferences are idiosyncratic. When I find other devices that I enjoy, I'll gladly talk about them. . . until such time, I am comfortable speaking about what does not play havoc with my musical enjoyment.
At this point I am intrigued by the potential of GamuT, Belles, an upcoming Wired4Sound reference device, and Chapter Audio. . . all more or less green energy efficient devices. If they turn out to be synergistic with my system and with my ears I'll definitely write about them. . . until such time, whoever insists reading my scribblings may have to bear with the little I know and love (grins!)