Doc said, that is a pretty sweet build. To answer your question about it playing BF4 - yes. I have a lower spec PC (running AMD FX 8320 and R9 270X) and I get over 60FPS on high settings (drops slightly on some maps). You will be able to get a decent frame rate on Ultra with this beast.
Also, don't listen to the people who are saying to get Win7. You get better performance with 8.1 (especially in the newer games such as BF4). If you don't like having the task bar like Win7, then I'd highly recommend getting StartIsBack - real start menu for Windows 8 and Windows 8.1. It gives you all the performance of 8.1 while getting the looks and features of Win7.