First things first with this.... that PSU is under powered. Use calculators like this to get an idea: [link] or [link] The asus is telling you what PSU rating you need while the thermaltake is telling you what continuous power you'll need.
So, that said, the seasonic you have there is enough power... but I think it would be a good idea to get the X650 for the possibility of adding more GPUs/other shit in the future.
Bitcoin mining is a waste of time and money. You will spend significantly more in electricity and hardware costs running this machine than you will make back in bitcoins. You really would need an efficiency-centric build for that to become profitable at all. [link] and [link]
Assuming that you can just double the rate of a single 7770 (which is optimistic) and an electricity rate in NZ of .16USD/kWh (which I looked up and is an average). You're looking at a power draw of 400 watts or so when you're running 100%. Even if you somehow committed a crime against physics and ran at 200W you're still losing money. Something to think about.
You might want to get a smaller HDD for your OS to sit on and use the 4TB of storage for storage and shit. I would suggest a 128 or 256 GB SSD.
Linux will only be a problem if the software you want to run doesn't run well on Linux :3 I'm looking at the video editing stuff as being potentially a pain in the ass with that.
Finally, don't install the LG optical drive in the case. It'll look uglier than sin itself. Just run the wires and have it in there loose with the side of the case off until you install w/e and then unplug it if you are using the CD/DVD drive often you should get a better internal drive. I also would consider getting a better case with better airflow. Especially if you're running these video cards hard for long periods of time.