You also don't have to actually "build" it yourself if you aren't so inclined, many custom gaming PC shops will assemble it for you for free or a small charge. I've been dealing with a local company in Calgary since I moved there in 94, and bought my first P200 from them, Memory Express. The last couple of systems I built I didn't bother actually doing it myself, as for 50$ they put everything together, installed the OS, and updated all the drivers to current versions for all the hardware. Then they let it sit for a day or two to ensure nothing just zaps, and then they let you pick it up. I'm sure most places will do this for you as well. It's not that I don't like putting my own stuff together, or that it's difficult, it's just a safety margin for me so that if a: I break anything or b: something is defective from the factory, I don't have to worry about it. 50$ for the time it takes to assemble, install the OS, and find and d/l all the drivers for every bit of HW is well worth it IMO.
This way I have the best of both worlds, I don't have to buy an off the shelf POS, nor do I have to pay 2 or 3 thousand for a box full of parts, instead I get a fully functioning and up to date system that is basically plug and play other than my headset, USB controllers, etc.