i5?
i5 for quickbooks, spreadsheets, and office? What's wrong with a Core2Duo, an i3, or an AMD chip? Seriously, you don't need much CPU power and new laptops will kill your budget. SSD's for the laptops should be a little more durable than spinning disks.
As for the NAS, yeah, but more like 4 bay, RAID 5. Just remember that RAID is NOT backup.
Or... how about a full-featured router? My Linksys E3000 with dd-wrt has all the NAS and FTP features I could want. You could put an external 3TB hdd on it. Then get another one to be a backup for that one. Ideally, you'll want some decent wired/wireless networking between 2 laptops and the file storage. Networked printer? or just shared?
