I was going smaller, but that case will work with the equipment I listed, but you will need to purchase a power supply separate I would recommend around 300 watts... and get the measurements of the power supply as that case supports one up to 180 mm deep.... I had a desktop case like that for my htpc at one point (when it was micro-atx instead of mini-itx)... ended up trashing it think it was the nmediapc one on the page lower down.... also grab measurements and make sure you want something that big 5.91" x 17.32 x 8.74 vs 10.87" x 6.93" x 8.74" for the two silverstones I listed.
it is a nice case and at this point I would say with no PSU included it comes down to aesthetics and cost... pick what you like and can afford... should be a pretty beastly htpc... check measurements and you might be able to put the 560ti that was recommended in there too... but that will more than likely be louder (another important consideration with htpc) than the low profile 6670 I suggested.
i3 2100 with the setup I gave would work fine. With the a8 3850 from what I understand you could probably forgo the video card and use the on die one... Also with the other case you mentioned you would have to change out the blu-ray drive I suggested because that is a slim drive made for smaller cases/laptops...
I would say skyrim should be no problem because it's pretty cpu bound, not sure about modern mw 3, but there are videos of people with the 3850 playing it on youtube, unfortunately I'm at work so I can't exactly review it and let you know... one of them seems to notate that they're getting about 40fps though.