All depends on what you're doing with it, but that seems like way overkill for a NAS. NAS is generally more about disk (and potentially memory) than it is about CPU. And a board with WiFi? Honestly your NAS should be hard wired into the network and your clients access could be either WiFi or hardwired, but your use may differ than mine.
It does appear that a CPU price is not included in your list, not sure if that means you already have it or what, but if you don't I wouldn't waste the money there. If anything you could throw more memory in there, but I also don't see much point in that unless you plan on running FreeNAS which 'requires' it.
Here's what I would start with around your budget:
PCPartPicker part list:
http://pcpartpicker.com/p/dm6rgs
Price breakdown by merchant:
http://pcpartpicker.com/p/dm6rgs/by_merchant/
CPU: Intel Pentium G3220 3.0GHz Dual-Core Processor ($47.99 @ SuperBiiz)
Motherboard: ASRock H97M Anniversary Micro ATX LGA1150 Motherboard ($51.98 @ Newegg)
Memory: Crucial 4GB (1 x 4GB) DDR3-1600 Memory ($14.99 @ SuperBiiz)
Storage: Western Digital Caviar Green 3TB 3.5" 5400RPM Internal Hard Drive ($91.99 @ SuperBiiz)
Storage: Western Digital Caviar Green 3TB 3.5" 5400RPM Internal Hard Drive ($91.99 @ SuperBiiz)
Case: Antec NSK4100 ATX Mid Tower Case ($36.99 @ SuperBiiz)
Power Supply: Corsair Builder 430W 80+ Bronze Certified ATX Power Supply ($19.99 @ Newegg)
Total: $355.92
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-08-09 08:09 EDT-0400
Add drives until your budget is used up.