I used Amazon Japan for almost all of the components and, while I didn't use Prime, shipping is super cheap and fast here. It took two days to get everything and costed about the equivalent of $10 total for shipping. To give you a better idea, my case, a big Fractal one, shipped separately and costed 50 cents in shipping.
If I ever move back to the States and am in need of another PC, I'll definitely be going the Studio Cat route, but I'm glad I was able to build this one successfully.
Speaking of, I need to update my signature to reflect my new rig's specs! I'll do that tonight :)