I agree, build it yourself, the experience is invaluable and it is cheaper then buying it from a company. I just recently built a pc (rig 2) for my father, and the experience was very useful. The only hiccup I had was that I bought a cheap psu and it blew up, (luckily my components survived
), but I see you have chosen a very good psu.
As agent said allocate plenty of time for building it, about 1 to 2 hours to build it. Make sure also no one disturbs you. Theres nothing worse then kids jumping on your back while you trying to fit in a motherboard.
And if you cock it up, you can always come back here for help.
good luck