I highly recommend getting R9 280x cards, and stay away from the R9 290x if you can (the noise and heat is unbearable). Sapphire cards are the best, but Gygabyte is the second best option.

The optimum setup is 4 GPUs, and you don't need double PSUs, just one Cooler Master 1200W will do a perfect job.

Aluminum frame is much better for dissipating heat and thus extending life shell of GPUs. It's also much easier to put together and fix things, compared to tight spaced plastic boxes.

I have a step by step video tutorials for building the rigs, which you can easily turn into a full blown mining farm like shown on my video. My design is cheaper, easier to build and runs more stable, cooler and quieter than the one in the youtube link the OP posted.