at the recent Bass Player Live NYC this past weekend, i got to try Ashdown's new Mark King signature MK500 head, and not too shabby! very rich, fat, and yet spoke rock like no other. moreso than any Ampeg. besides the color, how does it differ from the AD600 head? has anyone tried the AL-ADRP1 preamp? wonder how it compares to the ol' RPM-1. UK TB'ers speak out!