I have lots of piercings, too. Large, extensive tattoos and lengthy sessions still hurt. You have two small ones. You'll know pain when you actually get a large tattoo. And no, the one you're talking about getting on your thigh isn't large. I have no idea how you can possibly get all the detail required in a phoenix into a 5 by 6 tattoo, but I'm guessing your artist will discuss that with you. Will be interesting to see what he comes up with.
Have you posted any photos of your first two tattoos? Don't remember seeing them.