Help Me Build a PC! Please!

I'm looking to build a PC. I don't want to buy one because 1) I want to build it myself and 2) I'd like it to fit my exact needs. Below I'm gonna list the things I'd like and things I can do without and even some things you may suggest that I plan on adding later on. I'm on a budget of around $500-$700.

The PC will most likely sit next to my TV which is a 60inch Vizio LED. Connected to that TV is a XB1, FiOS box, and a Apple TV. Soon all those will be connected to a Onkyo HTS3500 to use as my surround sound and receiver. I'd like to plug my PC right into my receiver via HDMI. Sometimes the PC will be hooked up to my 25inch LED monitor on my desk, but I'd like it hooked to the TV usually.

The PC will mostly be used with Steam Big Picture Mode. I don't plan on playing more of the newer games that are on consoles (Titanfall, BF4) on it because I'd rather play those on XB1 even though I know those games look better on PC. I'd like a graphics card with the power to play those games, but playing them on Ultra is not a necessity. For me, the machine will be used to play games like Don't Starve, Elder Scrolls Online, Skyrim and probably the next Fallout and games that I find on sale that I missed out on. Left for Dead 2 is probably something I'll play a lot of for instance. Hopefully I make sense on this. I think a mid-range card is suited best for my situation. Plus if I ever want something more, I can just update it.

The case needs to be something in the smaller world. I've seen some nice "HTPC" cases that are nice and square. Looking for something black. Nothing flashy. Space for everything.

I think starting out with 8GB of memory would make sense, and upgrading to 16GB soon thereafter.

I'll be using a Xbox 360 Wireless PC Kit to game with. I really am not a keyboard and mouse player. Just can't do it. I know, I suck.

Motherboard wise, this is where I know nothing. Tell me what I need for my needs. I want to go HDMI into my receiver so that the PC's audio can be pumped through my surround sound (if that's possible). Will the picture come out fine on a TV my size?

Processor. Like the graphics card, I don't need something crazy. INTEL, AMD. Don't care. Looking for something that works for me, gives good performance for the price. I'm not gonna be over-clocking the thing. (Do you over-clock processors? I'm such a noob.)

Disc Drive. Not Necessary. This day of digital age, CD's and DVD's are useless. I have my receiver and XB1 to watch movies. If the case has a slot for one, great! I'll add one down the line. Doesn't have one? Whatever.

I have keyboard, mice, and a Windows 8 key. No need for those.

The reason I ask for help is because I've never done this before. I go on Newegg and see 5000 motherboards and have no idea what I should be buying. Am I overpaying? Am I buying something that will fry when I launch Skyrim? I'm sure the Verge readers have built more PC's then I've owned and seen, so I come to you.

I'll respond to any and all questions that will help you help me!