mATX vs. ATX

I am building a gaming/editing (video/photo) PC and I've going back and forth for months (many of you have helped so much). Now I want to go back to the mATX vs ATX argument. Should I only get ATX if I want to SLI? I don't want to SLI but I do want to OC a little bit. I was thinking about the gtx 780 but should I do mATX and consider an even better GPU (the Titan is on my mind now, haha). Here is my build so far minus extra case fans:

[PCPartPicker part list](http://pcpartpicker.com/p/2K7LX) / [Price breakdown by merchant](http://pcpartpicker.com/p/2K7LX/by_merchant/) / [Benchmarks](http://pcpartpicker.com/p/2K7LX/benchmarks/)

Type|Item|Price
:----|:----|:----
**CPU** | [Intel Core i7-4770K 3.5GHz Quad-Core Processor](http://pcpartpicker.com/part/intel-cpu-bx80646i74770k) | Purchased For $219.99
**CPU Cooler** | [Phanteks PH-TC14PE_BK 78.1 CFM CPU Cooler](http://pcpartpicker.com/part/phanteks-cpu-cooler-phtc14pebk) | $74.99 @ Newegg
**Motherboard** | [Asus Maximus VI Hero ATX LGA1150 Motherboard](http://pcpartpicker.com/part/asus-motherboard-maximusvihero) | $189.99 @ NCIX US
**Memory** | [G.Skill Ripjaws X Series 16GB (2 x 8GB) DDR3-1600 Memory](http://pcpartpicker.com/part/gskill-memory-f312800cl10d16gbxl) | $139.99 @ Newegg
**Storage** | [Samsung 840 EVO 120GB 2.5" Solid State Disk](http://pcpartpicker.com/part/samsung-internal-hard-drive-mz7te120bw) | $89.00 @ Amazon
**Storage** | [Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive](http://pcpartpicker.com/part/western-digital-internal-hard-drive-wd10ezex) | $59.99 @ Newegg
**Video Card** | [Asus GeForce GTX 780 3GB Video Card](http://pcpartpicker.com/part/asus-video-card-gtx780dc2oc3gd5) | $499.99 @ Amazon
**Case** | [Fractal Design Define R4 (Black Pearl) ATX Mid Tower Case](http://pcpartpicker.com/part/fractal-design-case-fdcadefr4bl) | $88.98 @ Newegg
**Power Supply** | [SeaSonic G-750 750W 80+ Gold Certified Semi-Modular ATX Power Supply](http://pcpartpicker.com/part/seasonic-power-supply-ssr750rm) | $119.99 @ Newegg
**Optical Drive** | [Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer](http://pcpartpicker.com/part/asus-optical-drive-drw24b1stblkbas) | $19.99 @ Microcenter
| | **Total**
| Prices include shipping, taxes, and discounts when available. | $1502.90
| Generated by PCPartPicker 2014-01-30 06:25 EST-0500 |

Any help would be awesome!