I have a FA .475, a FA83 in .454 with a .45 Colt Cylinder and a .45 Colt FA97. The .475 and the little FA97 get shot a lot. Now that I think about it, I've been seriously negligent by ignoring the .454/.45 -- think I'll have to rectify that.
If you already have two .45s, the .475 is a great choice -- one of my all time favorites. You can load it to whatever comfort/power level you desire. For the most part, I run mine with 400gr LFNGCs at a chronoed 1,140 fps. You have to pay more attention with heavier loads to keep the barrel off your hat brim (or forehead as the case may be).
FWIW,
Paul