We do a lot of video on a commercial basis. Most of your machines don't have Firewire but do have USB2.
You can always add a Firewire PCI card later if you find you need one.
Don't go over the top buying things that either you don't need or don't know what they are.
Having nineteen or so machines going, quietness is important. We tend to use Antec Sonata cases fitted with a bespoke soundproofing kit from QuietPC.