"Bullseye competition is also a great way to start if you have a full size .45 and a .22, but does not accomodate other calibers."
It does. There is a stage in Bullseye matches for "centerfire" pistols, in addition to the .22 and .45 stages. (Three gun matches) Any centerfire .32 cal and larger is OK. It's true, though, that many shooters use their .45s for the CF match as well as for the .45 match.
Pete