Not to burst your bubble but thats interesting that they'd put a 1000W PSU in your system when 600W (fairly conservative) is plenty. This means your PSU is not going to achieve its optimal efficiency.
Also, depending on whether your 2tb hdd is a 5400rpm drive, I would grab a 120-128GB ssd (~$160 on sale) and install the OS on it, just skip the caching altogether. Heck, I'd recommend that even if the 2tb is a 7200rpm drive. SSD caching is going to fall between hdd and ssd performance-wise. For the price of your system (~$1700?) it would be a shame not to have the OS on an SSD.
I also agree with steelcity. The pride incurred in the "I built that" concept is a huge motivator to build yourself, even if it does involve some headaches. Overcoming obstacles (as long as its nothing serious and costly) only adds to the feeling of accomplishment. My first computer was purchased from ibuypower.com and I was very pleased with them as well. I occasionally price check custom build systems on their website and the price difference is oftentimes negligable. But if I purchase from them, I can't say "I built that"
All else aside, it looks like you have a very potent system. Congrats.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 120 GB Vertex 3 Max IOPS, 2 TB Samsung EcoGreen F4, 8GB 1600MHz G.Skill @1.25V, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Hand-Built Wood Case