Help me build a PC...or two

The main game her and I would play together would be WOW, but I'd like to have it open ended so we could possibly play fpses together or future MMOs that have higher reqs. It comes down to me really needing at least one more computer so we can play together. I figure I might as well make something in the midrange so it'll last a while and she also likes to do a lot of video editing. I'm wanting a DX 11 video card, probably at least 6 gigs of ram, probably an intel i5 or i7 processor, and that's where my knowledge drops off the face of the earth ;P.

I'd love to buy a premade pc so it'd save me the work, but it really seems like most of the premade gaming pcs are just shitty or way too expensive. They're a luxury good and pc manufacturers put a big premium on them .