Firewire 400 is only slightly faster than USB2.
The iMac 2009 had Firewire 800...
iMac (Late 2009) and iMac (Mid 2010): External features, ports, and connectors - Apple Support
(most of them are CPU-limited to much slower speeds).
CPU limited ? Most of the cheap ones home-users buy have nasty slow drives in them too !
With Windows Server 2012 R2 NIC teaming and RAID6, voila: super speedy reliable access (but maybe a bit overkill for your needs).
Oh yeah... until recently I had a dusty old second-hand HP MSA 1000 with 14 x 15k drives and dual hot-swap raid controllers and power supplies
That thing was built like a brick crapper I tell ya, the only thing that needed occasional replacement were the drives, the rest of it ran like Swiss clockwork, I tried to kill it with seriously risky stuff like live online firmware upgrades, but it still wouldn't die ! However times have moved on and modern stuff uses less energy and runs quieter !
So to your cruddy old Wind-blows tower, I say
