Be aware that when picking PC parts - AMD/Intel or ATI/Nvidia, that you should do your own research and buy stuff that meets your needs. If you want a PC for purely games, I'd stick with Intel ~something like an Intel Core i5-4670K would be good place to start.. then you'd want a good motherboard, a quality power supply (650W+), a high performance graphics card (AMD HD 7950 is an excellent card and if you can overclock it, it can pretty much hold its own against a GTX770. Or if you plan on leaving it at stock GTX 770, GTX780 would be a solid choice) and at least 8GB of dual channel DDR3 1600Mhz RAM or higher. For other stuff like encoding and multitasking you might find more value in an AMD build.
Oh and you might want to have a look at which one is more open to upgrades paths in the future. For example, If you're looking to buy a Intel powered PC you'd probably want to go with Haswell, as this is their latest CPU (socket 1150) and will most likely be supported until the end of Broadwell (their next in line for desktop CPU's).. well until Skylake - which btw won't be for a while. Same goes for AMD. The current FX series CPU's are running on Socket AM3+ and is still going strong, so if you decide to go with that then the motherboard you buy now (on AM3+) will support their next generation CPU (Steamroller). Something to keep in mind if you decide you want to upgrade your processor in the future.
