I'll recommend something different from the above 2 rigs, a complete miniPC instead. SSD as standard, additional HDD storage optional.
Mini PC barebones: Zotac ZBox ID18 w/ Intel Celeron 1007U - $199
(local link: [Unboxing] Zotac Zbox ID18 - $199 SFF Barebone PC)
RAM: Crucial/Kingston 8GB 1600MHz SODIMM laptop RAM - $93
(4GB actually enough but 8 is nice to have anyways)
SSD: Samsung 840 Evo 120GB - $138
(one nice snappy HTPC)
Wireless KB&M-in-one: Logitech K400r - $55
(best value keyboard with touchpad)
Total:
$485
Optional Ext. Storage High Capacity: [4TB USB3.0] Hitachi HGST Touro Desk/Seagate Expansion Desktop - $249/$230
Optional Ext. Storage Med Capacity: [2TB USB3.0] WD MyBook Live/Seagate Expansion Desktop/ADATA HV620 (2.5") - $177/135/$159