Ryan's steering you right. I've got a Synology 1511+ I've been using for a few years now, using WD Reds. That's likely more than you need/want, but I got it for the iSCSI, expandibility, and hot spare capabilities which you probably don't need. It also has a ton of other slick bonuses, Security Camera NVR, Multimedia services, web services, etc... Slick unit.
If you really want RAID 5, then probably the DS414, with 4x2TB drives (~6TB usable) you'd be at $875. But if you want to save some money you could just go for the WD My Cloud 12TB (mirrored config gets you ~6TB usable) for about $675.
I would steer clear of Buffalo for NAS devices, personal experience is clunky interface and less than stellar quality hardware.
Experience and opinion tells me to suggest Synology.