If the PC is truly only going to be for just AH so far as gaming, I wouldn't get an SLI setup like the higher end example here. I've had several SLI machines in the last 2 years, and have a 970 SLI now, as well as an almost identical system with a 980. SLI won't help you, in fact it may even cause less performance, or problems with SLI. Skuzzy recently explained how the lack of..motivation..for nVidia to create good SLI profiles for gaming companies- even really big ones - is a big problem right now. He also mentioned SLI and the new version of AH may not get along. So, make sure that you just go with a single GPU if - and I stress only IF - you're only going to be gaming at HTC.
Otherwise, excellent examples above for you to copy. Also, regarding NCIX/etc, the last couple PCs I've built I haven't actually "built" myself, I've just paid the 70 dollars to have the place I use (NCIX's competitor) do it, as the 70 is worth it for me time wise, plus they test it for 2 days, install all the updated drivers, and replace any failing parts immediately. It's a good option if you don't have the time or inclination to assemble all the parts.
