Need Advice on Inexpensive NAS Box

Hi everyone - I'm trying to put together a relatively inexpensive, moderate capacity NAS box and could use some advice. I've decided to build my own (instead of purchasing a NAS device, say, a DNS D-Link 323) since I've never built a PC before and would like the learning exercise.

Approximate Purchase Date: ready to purchase just as soon as I figure out what I want  

Budget Range: around $300US after rebates - not a hard limit though if the additional expense is worthwhile

System Usage from Most to Least Important: NAS

Parts Not Required: keyboard, mouse, monitor, speakers, OS (planning on using FreeNAS), hard drives (already have several close-to-new ones), video card (integrated is fine since I'll just need it for FreeNAS installation)

Preferred Website(s) for Parts: newegg.com & tigerdirect.com mostly out of ignorance, open to others

Country of Origin: USA

Parts Preferences: no real brand loyalty here, anything reliable

Overclocking: No

SLI or Crossfire: No

Monitor Resolution: doesn't matter as this box will run headless

Additional Comments: I'd prefer a smaller case over a larger one. GigE LAN a must, onboard preferred. Integrated video would seem like a must also; I don't want to pay for a video card that I'll never use outside of the 10-minute FreeNAS installation. Not sure if I need a front fan to keep the disks cool. Quiet would be nice, but proper cooling is more important; so long as it's not a jet engine it shouldn't be a problem.

Here's my first attempt, right around $300:

AMD Phenom II X2 555 Black Edition Callisto 3.2GHz 2 x 512KB L2 Cache 6MB L3 Cache Socket AM3 80W Dual-Core Desktop Processor
http://www.newegg.com/Product/Product.aspx?item=N82E168...

Foxconn A88GMV AM3 AMD 880G HDMI Micro ATX AMD Motherboard
http://www.newegg.com/Product/Product.aspx?item=N82E168...

APEX TX-381-C Black Steel Micro ATX Tower Computer Case
http://www.newegg.com/Product/Product.aspx?item=N82E168...

COOLER MASTER Silent Pro M600 RS-600-AMBA-D3 600W ATX12V V2.3 SLI Certified CrossFire Ready 80 PLUS Certified Modular Active PFC Power Supply
http://www.newegg.com/Product/Product.aspx?item=N82E168...

Rendition by Crucial 1GB 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory Model RM12864BA1339
http://www.newegg.com/Product/Product.aspx?item=N82E168...