A couple things. I like Gigabyte boards so I personally think you made a good choice there.
I don't see an OS listed. Do note it is illegal to use a Windows license that came with, or was bought for another computer. If the disk says OEM/System Builder, Upgrade, Academic Edition, or "For Distribution with a new PC only", then it is not transferable to a new PC (or upgraded motherboard). Only full "Retail" licenses can be transferred to new computers. Therefore I recommend Windows 7 64-bit (even if you decided to go with 4Gb, though I think 8Gb, as the "sweet spot" for Windows 7, is what you should stick with), or one of the many free Linux alternatives.
I am curious about that case and have been looking at it for myself. Please let us know what you think (like/dislike) about it when done. I do like that it supports a standard ATX PSU.
The problem with BluRay on PCs is that you must also have the necessary software to play BluRay disks on your computer and that costs extra, on top of the cost of the drive.
So if you have a BluRay player in your HT setup already, I would stick with that and go DVD on your HTPC. Note that Windows has built in DVD support but Microsoft would have to charge about $30 more for Windows to include the BluRay licensing fees in Windows - so we can blame the BluRay consortium and their outlandish licensing rules for that, and not Microsoft.
I would dump those fans. The last thing you want with a HTPC is to hear cooling fans rumbling when listening to quiet passages in a movie. If your folks have gone to the point of having a home theater setup with surround sound, believe me, fan noise will quickly become objectionable. 80mm fans tend to be noisy to begin with because they tend to move at a higher RPM. And sleeve bearings are junk - they are noisy and have a short (relatively speaking) life span and will begin to wear, and become noisier sooner. So especially in a home theater setup, you want quality fans with, magnetic, precision ball or fluid bearings. Look for the lowest noise level (dBA). If the bearing type is sleeve or not specified, avoid that fan. You want a good balance between noise and air flow. And avoid any with LED lights. Something like these
would be much better (plus I see Newegg offers a nice volume discount for even 2 fans).