I thought about the cpu cooler. I was thinking that I wouldn't have to overclock and the stock cooler would be ok, but you are right. The one you chose maxed out at 36 db which may be a little loud for the case. Finding one that does make the living room sound like a data center can be a beesh. But the cooler is not to expensive and it has variable rpm--good suggestion.
Ram can be bought for less cash, but everybody I've read on blogs and in reviews rave about crucial. It's only a couple bucks more. Probably not a terrible buy.
I wanted a Z87 motherboard with the capacity for crossfire, in case I got a real bug up my ass and decided to add another videocard at a later date. The GT780 draws 250w, so it would be cramp the PSU capability--its doable within the power budget, but would probably have to be upgraded as well.
Good eyes on the network adapter and the OS.
I am manic in my fear of Win 8--every time I have to support somebody on it, I can't find a damn thing. I think the win 7 premium maxes at 16 Mg ram so I went with professional to have the option to go to 32 mg at a later date. Does anybody know if I'm just blowing smoke out my ass on this little win 7 tidbit?
If you want crossfire then don't buy gtx 780 because it nvidia card which supports sli. For cross fire get AMD card like in your case it would be R9 290.
You are still buying expensive windows version.
If you are not going to overclock then don't buy any cpu cooler
The Corsair CX power supplies are their budget line and cheap out on some components. 750W is an odd size for your system too since it's overkill with one GPU but not enough for SLI. I would stick with either a higher quality 650W PSU like the one I suggested in my build or an 850W PSU if you're serious about SLI in the future.
As far as the OS goes, it really blows me away that anyone would want to go with an OS as old as Windows 7 on a new build. You said you have used Windows 8, but have you used Windows 8.1? There are some subtle, but very nice changes in 8.1. The ability to boot straight to the desktop is great. You can also use a program like Start8 if you really can't get over the learning curve of the start screen. I was very hesitant to upgrade from Windows 7, but I haven't missed it for a second. As strange as it might sound, I really like Windows 8.1. You just get used to using a couple keyboard shortcuts and it's really not bad at all.