Seriously though, if you want to concentrate on design and not not hacking/tweaking it is simpler to get a iMac. I know this sounds lazy but I always used to build machines with upgradeability in mind, and then I never did it. Maybe replacing dead drives or RAM, but you can still do that with an iMac.
BUT, if it's a hobby and interest, go Hackintosh. I love the idea of getting similar MacPro performance for under a grand.
Seriously though, if you want to concentrate on design and not not hacking/tweaking it is simpler to get a iMac. I know this sounds lazy but I always used to build machines with upgradeability in mind, and then I never did it. Maybe replacing dead drives or RAM, but you can still do that with an iMac.
BUT, if it's a hobby and interest, go Hackintosh. I love the idea of getting similar MacPro performance for under a grand.