I was wondering why the estimated power consumption was so low... Oh well, there goes that $16 savings... *sigh*
Cutting back on RAM, and reverting the case back to the Factal Core 1000 USB3, I managed to cram a 1TB Seagate Barracuda in there, which is probably the fastest 1TB mechanical around, only for about $2 more than your original $650 build, so I'm about $20 north of that. I noticed a huge split between Amazon and Newegg with the parts, despite them having identical pricing, so I overrode those with the same price to Amazon because they have much better packaging.
http://pcpartpicker.com/p/2WBrw