1) Why the ITX board? That is so expensive and... why is it needed unless you are using a very small case. Please explain.
2)What is the reason for the 16GB of RAM? 8GB is pleanty for gaming or anything else. If you know you are doing large video editing or something that specifically requires a ton of RAM, I would drop to 8.
3)All those nice parts and a little PSU. I'd beef that up a little. A good 500W at least.
4) The closed loop liquid is your call, but my opinion is they aren't any better than a good air cooler and you can get one of those for the same cost. However, this is preference and doesn't really effect much.