I had a cat along with my parrot but he ended up eating..... well not actually eating but he ended up killing my parrot when it hapen to get out of it's cage so I only have my new parrot now. It's kind of hard for me to keep all my pets in line without them getting in eachothers way.
I you want a reasonable sized snake, look into Ball Pythons. They are generally well tempered, easy to handle, and relatively small(5-7 feet, as compared to Red-Tail Boas which grow up to 15 feet).
Lots of folks like them because they have girth and stay a reasonable size. Furthermore, depending on how much you want to spend there are many different color morphs available.