Okay, after reading through all of the comments (seriously, you guys are awesome), I think I've more or less figured out what I'd like to build.
My budget is about $3k USD. I've already got a case and a cooling loop, so I'm basically going to be replacing the guts. With that, though, I've got a few questions.
1) You've mentioned getting 16GB of RAM to start with, and then upgrading to 32GB if it's not meeting my needs. Would a set of RAM (for example a 32GB kit) offer better performance than two smaller kits purchased seperately? I can't remember who told me this, but I was led to believe that there could potentially be issues when mixing and matching RAM, even if they're from the same manufacturer and the same speed, but different production lots. Is this true, or bad information?
2) I've pretty much decided on the MSI 290x Lightning. Amazing out of the box, and I can only wait to see what it will do when I get around to OC-ing it underwater. Can you think of anything better suited to gaming at that price? ($670 USD / £390)
2a) Follow-on question: The Lightning comes with a backplate, and it looks rather sturdy. Should I invest in a backplate from the manufacturer of the waterblock, or would stock be sufficient?
3) Is there any reason, other than its price or the fact that it's more power than I need, why I should choose an s1150 over the s2011 and the 4930k?
These questions aside, I think I've nailed down the build. It is for gaming at 1440p resolution, along with occasional rendering operations. The parts list is as follows:
Motherboard: Asus Rampage IV Extreme X79
CPU: Intel i7-4930K
Power Supply: Ultra X4 850W (Currently owned, otherwise the Corsair 850d)
RAM: Kingston Beast 32GB 2400MHz
GPU: MSI 290x Lightning
Waterblock for MB: EK ASUS RIVE Full Board Cooling Block Kit - Nickel
OS Drive: ADATA 256GB SSD / SATA 6.0Gb/s
Storage Drive: WD Black 3TB HDD SATA 6.0Gb/s (Owned)
Various Other Bits: 6 Meters of Acrylic tubing, starter kit for bending rigid tubing, 18 compression fittings, 270mm cylindrical reservoir, and a D5 pump to push it all.
Why 6 meters of tubing? Because I'm a slow learner, and I'd rather not have to wait for a second package of tubing to arrive, because I am not patient. And I had to buy 18 of the compression fittings because they come in a 6-pack, and I needed 14. As configured, the grand total is $2994 USD, plus approximately $40 USD for shipping and misc. taxes.
So, feedback? I think this is a more realistic build for what I'll be using it for. Though, I have to admit, I'm still probably going to treat myself to the Rampage IV Black edition at some point in the future. I'm a fan of the color scheme, not to mention the onboard sound card.
Again, I'd like to extend a genuine Thank You to all of the people who have contributed their knowledge. Honestly, I was sort of expecting something along the lines of "you're an idiot" or similar. So, to all of you, Thank you again for being patient with the new guy.