Your kit out would be a nice rig. I think you'd have more fun and building it would make it "yours" in a very different way.
Here's a few things to think about.
Do you think you want the i7 over a similar spec'd i5? Again, if this is a gamer machine, a mild overclock on the i5 will yield everything you need. The i7 (other than bragging rights) really helps in those tasks where you need hyperthreading (i.e. encoding, CAD work, etc.) an I5 is no slouch in these tasks either, but the i7 rules. Now in gaming, hyperthreading doesn't do much. So you might be paying for something you wont use / use infrequently. An i5-4670K is $240 vs the i7's $340. Use the extra cash other places (better monitor / SSDs, sound, etc.)
Graphics are kinda of a Ford vs Chevy thing, however, have you seen the recent price drops on AMD's cards?
For what you're dropping on that gtx 780, you could have a 7990. True dual GPU for an itx, twice the Vram, better 3dMark score, almost twice the floating point calcs, twice the shaders, (see a trend here?).
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202036 (includes 8 free games, and a great cooler)
-or -
look into a 7970
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202008 (truly a little behind the gtx 780, but $300! cheaper!)
or a 7950 overclocked:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127667 ($250 - almost $400 cheaper - this is my card, and it's does 1920x1080 all day long, but mine is WC and modded)
The whole matx vs itx is choice. I was mATX for a long time but now I run three machines, all ITX. So I like it. Now, if you've not made many machines, ITX can be smaller to work in. So if you go smaller, just take your time. Post here if you need help.
For itx, I would suggest you look at this: ($190)
http://www.newegg.com/Product/Product.aspx?Item=N82E16813132028
but if you want, you can do the ROG Asus, it has a few more bells and whistles, but it's $50+ ($230)
http://www.newegg.com/Product/Product.aspx?Item=N82E16813132039
Now, for an IVY (Z77), check this out. it's a good overclocker, and has a $20 MIR for a final price of $160
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131840
mated to a i5-3570K ($220)
If you want to try ITX check out this case (also Silverstone)
It includes a nice 600W power supply. Not modular, but will be good. About the same price as your case / power combo. A small mail in rebate for the next three days.
http://www.amazon.com/gp/product/B006L6ZHEG/ref=s9_simh_gw_p147_d0_i1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-3&pf_rd_r=06F4CRY1CCPDXSEJWAQY&pf_rd_t=101&pf_rd_p=470938811&pf_rd_i=507846
or with a window:
http://www.amazon.com/SilverStone-Mini-ITX-Mini-DTX-Certified-SG07B-W/dp/B003V8ATM2/ref=sr_1_19?s=electronics&ie=UTF8&qid=1377699604&sr=1-19&keywords=silverstone+itx
You have a good SSD. Depending on choices you make, I'd look at another one for games and / or a storage drive (like a 2-3TB 5200 rpm). Personally, I did a 16GB ram kit (2x8), but I do alot of photoshop, so it might not make as much difference for you.
Wheh - lots of typing. Your thoughts?
