Judge Kodiac
Welcome to one of the fastest growing segments of the shooting sports! Don't think you'll stop with only four firearms though. There are all those side matches; derringer, pocket pistol, and long range rifle.
Make sure you want to stay with .45 before you start buying. Quite a few shooters are turning to .38s though I like to ring the gongs with the big bores ( I use a pair of Vaqueros and an older Marlin 1894 in .44 Mag downloaded). Then of course for the single shot or long range rifle I have my Rolling Block. Though when Gunslinger is around the Rolling Block I have to keep an eye on him or my Rolling Block may get "lost"
Then there are the duds to be acquired. I'm still looking for a pair of batwing chaps. Plus another pair of pants and another shirt would be nice plus.....well, you get the picture.