1.) CPU. If you want my honest opinion, you can get twice the processing power for the same cost if you go with AMD. Find one of those CPU benchmarking sites, here's an example:
http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i5-3570K+@+3.40GHz
According to this, for less money ($199), you could purchase the AMD FX-8350 CPU and get about a 25-40% improvement in performance for 10% less cost. Of course you'd have to pick a different motherboard that is compatible with the particular AMD CPU you end up buying, but just my opinion. I never have and never will purchase Intel and I've always been satisfied with my computers. My opinion is when you buy Intel you are paying for a lot of their advertising instead of for performance. The only thing that matters is performance and price.
2.) CPU cooler. A year ago I looked very, VERY hard at a liquid-cooled system. Why? I wanted a high-performance, but whisper-quiet computer. I gave up on liquid-cooled because the performance of these liquid cooled systems actually performed worse than cheaper traditional air/copper CPU coolers from companies like Zalman, and in some cases the liquid cooled system was actually noisier than using air! If you are just doing it for the brag factor then stick with the liquid cooled, but if your goal is performance, take a second look at traditional air coolers. They perform as good or better, could be quieter, and probably a lot cheaper.
3.) Hard drives. If you can afford another $100, purchase a 128 gigabyte SSD drive to install your operating system and apps. Two years ago I purchased a $2,600 computer system. The bottleneck was the 7200 RPM SATA III drive. I ended up purchasing two 64 GB SSD's. It turns out that 64GB is simply not enough space for Windows 7/8 plus all your apps. 128 GB recommended, 64GB minimum but you will run out of space very very fast! SSD will speed up your boot times as well as seriously speed up your application loading times.
Also, I've purchased a lot of Samsung hard drives and they've all failed. I am not saying Samsung is a bad brand (I don't really know). In most cases the culprit is overheating localized near the hard drive. The hard drive gets crammed in a 3.5" rack in a tight space in your computer and creates a hot spot. Do yourself a favor and buy one of those Antec "spot fans" and point it at your hard drive. Also i highly recommend if you have critical data, either back it up regularly on DVD, on-line, or buy an identical second Samsung spintpoint and run it as a RAID mirror so if you lose one drive due to mechanical failure you will not lose your data.
4.) Power supply. 550 watt should be enough but double-check the power requirements of your video card.
Hope this helps, I've built 6-7 custom PC's in the past ten years and my opinions above are based on my own experiences. It sounds like you are building a nice system and it is going to do some kick-*** stuff for you if you just purchase the build you picked out! If you could only make one change and one change only, I would purchase that 128GB SSD for your operating system and games/applications.
. But down in the real world where computer budgets are $1k-$2k it's pretty even.