Hello!
I do not think going straight to board is worth it. An SSD even in SATA 2 will be much faster than any HDD on the market.
I'd get the W3680, I don't think the extra clock speed is worth the extra $, personally.
The PSU may be pushing it with a discrete powerful GPU. I'd think if it were an RX 480, it'd be okay though, as it only requires one PCIe 6-pin power plug.