Certainly check the video/photo software. Most professional grades will take advantage of Cuda cores on the NVidia cards, but don't take advantage of the Radeon or R series cards from AMD. Gaming can be better on AMD, but video editing and photo editing can generally benefit from an Nvidia card.
Seriously, I'd take a look at a laptop. You may find it handy to do some editing on the go, and there are certainly laptops with more power where you need it (graphics wise) that are more affordable that your specifications. Here is a link to a review of one such laptop:
http://www.pcadvisor.co.uk/reviews/laptop/3524083/gigabyte-p35w-v2-gaming-laptop-review/
I do a lot of professional video editing myself, and photo editing. When I decided to dump the gaming end, I decided to go with a laptop, because I find I need the portability at times, as it gives me the opportunity for more freelance video editing work (like going to a church and doing the editing there from their digital recordings, then heading to the next client.)
Building your own takes time, and you have to test your hardware if you want to be certain it will all last for the long haul. A prebuilt system has, as a general rule, already gone through the testing. While building can be fun, sometimes it can be even more fun to get a laptop that you can hook up to a monitor/keyboard/mouse at home (docking it), then unplug it, put it in your bag, and kick back at a coffee shop with good Wi-Fi and surf the net while you check out the local scene. Get a nice, high end, good-looking laptop, and you may turn a few heads if you need to meet that special someone. Though I've noticed some girls only notice you if you have a new Surface Pro 3, which is a pretty high end device as well.
Best of luck, whatever you decide.
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