If you live in the US/CA I'd assume Newegg.
So here is my take
Total: 362.93$ + 14.52$ Shipping
Well Shipping is to my address, so... Could be different where you are.
Umm the reason for the CPU is because with 3 cores you'll be able to multi-task, it also saves you some money going with AMD. Also the fact that the Rana is a pretty good CPU and it defiantly is no slouch. The Motherboard is because the things you want to do with this new computer only require the bare minimum of a graphics card. So with this onboard video you save money, plus you can use any monitor/TV running 1080P. Also, the board offer USB 3 and will future proof you for next year. The ram, well it's in a combo, it's cheap and not bad at all for the price, what more could you ask for. The PSU is because it's a great brand, great effiency and probably the best "cheap" PSU out there. You don't really need anymore than 500 watts should you follow my build. The Case is just a great case, intake/exhaust fans just what you need. Plus it's not a bad brand.
Umm anyway, your going to have to spend the rest on the OS, so assuming you pay full price it's 80$-ish so total would be around 450$-ish. Which country do you live in?