If you're planning on having a gaming setup I'd say go for a custom PC setup. It'll be entirely up to you whether you want to stick with the whole AMD/Radeon combo or Intel/Nvidia.
I never thought I would actually see such a thread. Are you serious? Why would you spend that amount of money on a mac? Just get an iMac or macbook pro if you want a mac, the mac pro is completelt overpriced.
I mean, if you want a PC that is user friendly and easy to modify, go with the mac pro.