I don't think there would be a problem changing their names. I'm always coming up with new nicknames for my little ones and they seem to catch on really fast. At the beginning, say the new names often, especially when you are petting or interacting with them, and offer them a little treat if they look at or respond to you or come to you when you call them, and they'll not only learn it fast, they'll like the names too!

Hey, I hate my name, but like it a lot better if someone gives me chocolate when they say it.

I once read somewhere that in naming animals, especially cats, the best names are ones with a hard consonant sound to them. The article said that's what they recognize, not necessarily the whole name, and the sound should be different for each cat so they learn quickly who's who. For example, two cats named Callie and Corinna might confuse them, but Callie and Zelda, it's easier for them to differeniate between the "K" and "Z" sound.

Don't know if it's true, but I read it once!