New build for 2D editing and 3D rendering - 3-4K budget

You already seem to be quite knowledgeable in what your doing, the rig as you have specced it out so far is fairly good. Some things I would change though.

- Dont bother with Dominator memory, your paying near double the cost for a shiny heatsink. A kit like this is a far better option, just get two of them.
http://pcpartpicker.com/part/corsair-memory-cml16gx3m2a1600c9
Also unless you can get it cheap, dont pay extra for RAM faster than 1600Mhz. The difference between 1600Mhz and 2133Mhz in benchmarks is minimal, in actual usage it wont be noticed.

- 1200W is a bit overkill, for a rig like that, would say go for an 850W unit.

To your questions.

- Motherboard you picked is actually fairly good, if a bit overkill.

- Modern motherboards come with a decent onboard sound card, fine for what most people want. If your running 2.0/2.1 speakers or sub $100 headphones, then I recommend an ASUS Xonar DG or DGX respectively at most. If you have an audio setup worth dropping a few hundred on a good sound card, then chances are your already enough of an audiophile to know which one to get.

- What do you mean by the water-cooling comment? Just there are two kinds, and they vary quite a lot in cost, complexity and performance.

CLC's (Closed Loop Coolesr) are your Corsair Hydro series type units, they come pre-assembled and all you do is hook it up to the rig and plug it in. No real assembly required, no maintenance other than dusting the rad.
However, they perform no better than a big air heatsink could manage. For instance that H100i is roughly equivalent to a Noctua NH-D14 for performance, which is a good $20-30 cheaper.

Then you get to your Custom Water-Loops, which is where you buy each part (Pump, radiator/s, fittings, CPU block, etc...) seperately and assemble it yourself. This costs and requires maintenance the most of all the "normal" cooling solutions, but you get unparalleled performance and if you do it right, will be very quiet. Also far greater flexibility, you can cool near everything with water if you wanted.
If your interested in custom-water cooling, I suggest you read the WC sticky.
http://www.tomshardware.com/forum/277130-29-read-first-watercooling-sticky

The hair combs they glue to that RAM might get in the way of the cooler, would go for a low profile option like this.
http://pcpartpicker.com/part/corsair-memory-cml32gx3m4a1600c10

Otherwise looks fine to me.

This G.Skill kit is the equivalent to the the Corsair RAM I linked above.
http://www.prisjakt.nu/produkt.php?p=1334931

All good man, better you ask the questions now than after you'v spent all your money on a mis-informed decision.

^ Depending on when that was manufactured, it could be a very good monitor to get your hands on. If thats the 2B version manufactured in February last year, the thing can potentially overclock to 120hz.