I went with 2x2 because it's cheaper - 8GB is just about the ideal spot.
You could get that as a 500GB drive, but I think it would be all of $6 cheaper.
As for the case, it's a very personal thing; I personally like minimalistic cases, so you're on your own for that. That youtube build is a good option, but the CPU is significantly less powerful; it's up to you whether you want that with better graphics or be able to upgrade graphics 2 years down the road while keeping that CPU without a bottleneck.