I have the pro 600 as well, and it's a dream. It will take 3 cake mixes at once, and I can do two batches of NFSC or MMF without a problem. If you tend to bake a lot at once, I would recommend it. If not, then the Artisan will probably do you just fine.
I'll second what someone said about checking the clearance between your counter and cabinets, though. There's only one place on my kitchen counter that I can actually use mine, so it lives there, but it's not where I would have chosen to have to work.
And keep the splatter guard handy. The only complaint I have about the 600 (and I'm not sure if it's just a KA thing or not) is that it will splash up with the least little thing. And if you dare to dump more than a little bit of powdered sugar in at once... just be prepared to look like a ghost.
But I wouldn't trade mine for anything.