I would not go with mac simply because premiere pro with adobe production studio works on pc a lot better.
build your self a pc with quad cpu, a lot of hdd space, use ddr3 and least 2gb, good case that has a very good cooling capability, video card you can go with 8800 or quadro cards with 512Mb of ram, or use matrox rtx2, and dual monitors (2.5-3k), then add a production studio (1.6k) and you will be uder 7k, and if you want you can buy your self a bluray burner (.5k)