ive been using power amp all week. i really like the interface. much better than stock htc players and i even like it more than doubletwist. very nice player.
i grabbed an app called 'sound manager'. it gives you sliders for all volume controls on the phone. system, ringer, notifications, media, alarm, and in call. The one thing i missed from my ipod was a software volume slider when music was playing and this fits the bill and then some.