Hiya Kas!
Not sure what editing software you'll be using but i'll give you advice on the idea that you'll be using either Sony Vegas or Adobe Premier. Adobe employs the GPU for a few tasks such as editing and does the job of compiling /special effects/ in the rendering phase (i.e. title sequences, transitions, most after effects fancy graphic stuff), so for that reason and also for gaming, I would hold off on that 750ti and save a little bit more for a 960. Both editing software I mentioned work best with the most cores you can buy, so the i5 for $199 I think is a solid choice for the price. I would /seriously/ recommend buying a second hard drive where you will render your video to. (i.e. Your source videos are on drive C: but you're saving the final product to drive E:, a physically different hard drive). Adobe /really, really/ recommends this as the whole process of creating and saving videos from the same drive will /over time/ accelerate the hard drive's lifespan (i'm paraphrasing what adobe states). You're free to buy whatever hard drive, just make sure it's read/write speeds at /least/ match your main hard drive #nobottlenecks. I recommend some small SSD, that way you get blazing ssd performance, but it won't break the bank. Aside from that you /could/ find a cheaper case if you're not sold on the S340, maybe a
Corsair -
http://pcpartpicker.com/part/corsair-case-cc9011086ww
NZXT Source 210 -
http://pcpartpicker.com/search/?cc=us&q=source+210
So, in short, good pick but seriously adding a second hard drive and I think you could save a few bucks on a different case. Everything else looks great!
