I'm really only about a '6' on the Geek Scale, so I'll try to make this as simple as possible.
SCALABILITY: This is Geekspeak for E-X-P-A-N-D-A-B-I-L-I-Y. You want to set-up archives that grow. Most photographers started out using single external drives, but as your archives grow, so does your collection of individual drives. A friend of mine went down this route until he had a "Great Wall of Drives" with 40 LaCies Daisy-chained with 40 individual power sources as a case study for "Fire-Code Violation."
You DON'T want to go down that road.
You also do not want to be plugging drives in and out of enclosures because you are too cheap to buy enough enclosures. 2-Bay enclosures are meant for backing up files while you are on the road. PERIOD. There is no other long-term use for them. They give you no ability to expand. You will have to add more drives in the future. Just accept it.
In your case, you have room for 3 more internal drives and that's where I'd start. You do NOT want to keep you data on you start-up drive with you applications. Get all that stuff onto a PAIR of matched internal drives - you have the space. New Egg has Western Digital 750 drives on sale for $149.
HARD DIVES TO TRUST: Seagates are great. Western Digital have shorter warranties but also hold up very well. Hitachi's are great IN a Mac, but have issues in external drives because they are very slow on start-up and can time-out in an external enclosure.
On the other hand, I've never heard good things about Maxtors so I avoid them.
LaCie doesn't make drives they buy from all of the above depending on which of the above gives them the best price on a given day, so you never know what guts your are getting. So in the words of Clint Eastwood, "You gotta ask yourself, Do you feel lucky punk?"
If you buy drives from
NewEgg like I do, you'll notice they have like five identical listings with differences like "OEM" and "retail." This refers to the packaging and as one of the drive manufacturers told me, packaging has nothing to do with performance so buy the cheapest you can find since you're not going to keep the box anyway...
CONNECTION SPEED:
WICKED FAST: Fiber Optic, such as Apple X-Serve RAID. Also wicked expensive.
VERY, VERY FAST: SCSI - makes you wonder why it's all but obsolete.
VERY FAST: SATA used on most Internal Drives or SATA enclosures
KINDA FAST: Firewire 800 and USB2 - USB2 is slower than FW800 on a Mac, but faster on a PC.
NOT-SO-FAST: Firewire 400
SLOW: USB
SLOOOOOW: DROBO. Ok, I know Drobo is a drive enclosure not a connection type but for some reason it's slower that USB2 should EVER be...
EFFEN SLOW: NAS Ethernet based NAS is NASty slow. Like watching paint dry...underwater...
If you're on a Mac, no matter what kind of drives you're using, step one is formatting the drive in Disk Utility so that it's compatible with your current OS. Disk Utility can be found under Applications>Utilities>Disk Utility. I run Disk Utility to "Repair Permissions" on my boot drive every time I install or upgrade software, so I keep it in my Dock.