ck: if you don't want to go with jhm's advice, which is quite sound, get yourself a lightweight Springfield in 45. As for the 10 round magazine, either Chip McCormick or Shooting Star or Meggar (I think) makes a 8 rounder which gives you 9 with one up the spout and still fits flush.
Deputy, Zeus and JeffG all gave you solid advice. I just prefer the plain ol single action autos, but Kimber is sort of the cream of the crop and will cost you and the others, the Sig and the Glocks don't have the types of trigger actions I prefer on a 45. A good used Colt is better than a new Colt and a Springfield is better than both, IMHO. Mikey.