Herco is awesome with heavy cast bullets. I haven't tried it with 125's (Unique or Bullseye might be better with light bullets) but it should work if you keep to the upper end of the load data.
AA#7 is comparable to Blue Dot, but it meters better and doesn't have all of BD's nasty habits -- like pressure spikes and temperature sensitivity. I also got severe leading when I tried BD, and equivalent loads with AA#7 don't have that problem. YMMV.
Power Pistol is on my short list of powders to try -- but I have 16 pounds of AA#7 and five pounds of Herco, so I might not get to it for a while
