Rack Mount Windows Server

Hi, 
 
I am looking to upgrade from my very old Acer Aspire EasyStore with 4 HDD bays to something rack-mounted and much more powerful.
 
I was looking at this unit on ebay: http://www.ebay.com/itm/261256446386?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
 
Which will accommodate my processing requirements, but it doesn't do it for storage.
 
Right now I have Four 2Tb WD Green HDDs(EasyStore ran 32bit WHS) and my space is rapidly filling up.  I am also backing up on external 2Tb WD drives which is a pain.
 
What I'd like to have is some way to accommodate 16 internal WD 4Tb drives, so I can expand my storage space and also have backup drives right in the unit.  I wont be buying all 16 drives at once, probably 4 to start, but I would like to be able to expand as I need to.
 
Anyone know of a good way to accommodate this?  The server I linked only holds 4 HDDs in it.  I'd like to do a rack-mounted setup, but if there was a slick tower case that seemed to fulfill my expectations for the storage space, I would consider it too.
 
I'd like to keep the total cost under $2000, including 4 of the drives.
 
Thanks in advance!
 
-Jay