Well, parallels sets up a virtual machine for the OS to run in, sooo... performance is reduced. I use Parallels, but only to test new Linux distros. But, It is possible if your system is fast enough. Good luck!
Well, if I'm thinking about the Quad Power Mac, I think it will be. Plus, I'll only use Parallels for media conversion software, or any other software I can't get on Mac, so...