The hardware is nothing special.  Just an old motherboard and some memory I had left over.  Just search for rack mount server cases and you will find plenty of 10 drive cases in the $250.00 price range.  The hot swap-able drive bays run about $50.00 each.  Don't buy the cheap drive bays - they fail too often.  The main differentiator in my media server is the OS.  I'm running Lime Technology unRAID. 
Why? Because RAID was designed for UPTIME - not data security. Even with RAID you still need to back up your data. If 2 drives in a RAID array die (and it will happen) then the entire array is gone. 
Don't think 2 drives will die at once? Consider this - you are buying all the disks at the same time therefore all the disk will reach end of life at the same time. Making multiple failures a real possibility. 
With unRAID if multiple drives die the most you lose is the data on the drives that die. Everything else is totally recoverable. If a single drive dies then you lose nothing (as long as you replace the drive before another one dies) 
With unRAID you only spin up two drives at a time - the target disk and the parity disk=LESS HEAT+ LOWER ENERGY COST+ LONGER DISK LIFE 
unRAID allows you to use disks of different size - as long as the parity disk is the largest. (throw in a 750 GB for the parity drive and you can then add any size drive at any time) 
You can expand your unRAID array at any time - or - add a larger drive - copy data over from the smallest drive in the array - then remove the small drive and replace it with a larger - repeat!  
unRAID is HUNDREDS of dollars cheaper than any decent RAID card and allows you to run up to twelve disks. (11 + 1 parity) 
unRAID supports both PATA and SATA drives 
I understand that this looks like a paid advert - but no - I don't have any association with or financial arrangements with them - its just good shit. 
check out the unRAID website here: 
http://lime-technology.com 
and check out what they say about it on AVS here: 
http://www.avsforum.com/avs-vb/showthread.php?t=627605 
and here: 
http://www.avsforum.com/avs-vb/showthread.php?p=8585066 
The biggest complaint you will see regarding unRAID is that it is a one man operation and that he sometimes disappears from the unRAID forum for days at a time (does that sound familiar?) - or people will have a hard time setting it up if they don't use the recommended hardware but he has never ripped anyone off. 
HIGHLY RECOMMENDED - TWO THUMBS UP 
(just my opinion - YMMV)