re: Release of Steam Machines/boxes?

No on the cables, and on the fan filters,it depends. They do help reduce dust, but only if you have more air going into the case than coming out. If there is a higher exhaust pressure, air will be pulled in through other crevices/holes in the case, so the fan filters won't really be of any use. I would just hold off until the build is done, check your dust levels in a month, and then decide whether filters/different fan arrangement is necessary.

As for the motherboard, any board with a lot of reviews are going to have negatives. Some are legitimate failures, others are complaints about things they themselves overlooked, or just plain user error. As long as there aren't an overwhelming amount of negative reviews that have similar things in common.

However, one thing I just realized was that the NZXT case has front USB 3.0, and with that motherboard, you would not be able to use the front USB 3.0 ports at all unless you buy something like this. ($20, and has a header for your front USB 3.0)

Or, this ASUS board is $10 more (after rebate) than the ASrock and has USB 3.0.

Looks like you can get it from Amazon for $136.99 Prime shipping: LINK

And you can still use this $20 rebate form, bringing your total to $116.99:

Would The ASrock work with this cheaper Corsair case? Or ASUS motherboard with Corsair?

Yeah, that's a good deal on that case.

In bold is how my build looks so far.

PCPartPicker part list: LINK
Price breakdown by merchant: LINK /
Benchmarks: LINK /

CPU: AMD FX-8320 3.5GHz 8-Core Processor ($149.99 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: Asus M5A99FX PRO R2.0 ATX AM3+ Motherboard ($119.99 @ Newegg)
Memory: G.Skill Sniper Series 8GB (2 x 4GB) DDR3-2133 Memory ($74.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: Asus GeForce GTX 760 2GB Video Card ($249.99 @ NCIX US)
Case: Corsair Graphite Series 230T Grey ATX Mid Tower Case ($39.99 @ Newegg)
Power Supply: XFX ProSeries 750W 80+ Silver Certified Semi-Modular ATX Power Supply ($124.99 @ NCIX US)
Total: $849.90

Will finish up with the video card and powersupply by the end of the week.

Reading over your walkthrough, this build seems to fall pretty much in line with your pie chart. Amazing work on that, learning a lot

AMD FX-8320 3.5GHz 8-Core Processor/Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler: 143.80 + 33.24 - 21.5%
Asus M5A99FX PRO R2.0 ATX AM3+ Motherboard: 119.99 - 14.60%
G.Skill Sniper Series 8GB (2 x 4GB) DDR3-2133: 74.99 - 9.12%
Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive: 59.98 - 7.30%
Asus GeForce GTX 760 2GB Video Card: 249.99 - 30.41%
Corsair Graphite Series 230T Grey ATX Mid Tower Case: 39.99 - 4.87%
XFX 850W 80+ Bronze Certified Semi-Modular ATX Power Supply: 99.99 - 12.16%

Total: 821.97

Yup. Hope to have everything delivered sometime mid week next week.

don't have skype on my ipad yet, but can download it.