Can this Server be used as a SAS/NAS for a Domain controller setup?

With our new offices, i currently have a dual Xeon 2.4G with HT (400FSB) and a raid 6 of 6x 160G SATA harddrives +1 hotspare

The system does fine for what it is needed for, now going to our new office, and having a domain controller and AD and such, i have heard and read thing like you need a proper SAS or NAS for Server 2008 and such to be able to use an external data store.

Is there any way that i can use this server as the data store in some way so i dont have to drop $2k on some new SAS system?

You shouldnt have to have an external data store.

Maybe to work with Storage Server but 2k8 should do just fine with on board storage.

i am considering external because alot of files wil be used with roaming profiles for at leat 4 accounts that will be on the DC.

Also the AD/DC/DNS are on Dell SC440's that can only hold 3 harddrives (i could get a 3 in 2 5.25 box) but thinking external would be better performance wise.

Next question, will a Dell tape store work with this server as long as i get the right interface to connect it to?

http://www.dell.com/us/en/business/enterprise/pvaul_114t/pd.aspx?refid=pvaul_114t&s=bsd&cs=04