Um...first off, for forward compatibility, please don't buy anything without USB 3.0. New Macs have Firewire 800, not FW 400. And USB 2.0 is dog slow. Even if your current Mac doesn't have USB 3.0 or FW 800 or Thunderbolt, if you upgrade in the next few years, anything new will. You can use a USB 3.0 drive with a USB 2.0 Mac - it will just work at USB 2.0 speeds. For Firewire 800 you will need an adapter, and if it's that or using USB 2.0, I'd recommend you get the adapter as FW400 is faster than USB 2.0.
Given that, if you want the OWC drive, then I'd go with this enclosure:
http://eshop.macsales.com/item/Other%20Wor...ng/ME3QHKIT0GB/I don't generally buy pre-assembled hard drives because you never know what's inside until you get it. I usually buy drives with 3 or preferably 5 year warranties. I used to like the
Western Digital Caviar Black (still do like the ones I have) but the reviews lately haven't been as good at NewEgg as they once were. However, it still has a 5 year warranty, so definitely worth consideration. An enterprise class drive is probably overkill, though the price of these isn't bad, considering:
http://www.newegg.ca/Product/Product.aspx?...N82E16822148784Other options on the enclosure front:
http://www.newegg.ca/Product/Product.aspx?...N82E16817347039I've had good luck with Macally enclosures.
And I've also had good luck with Vantec enclosures, which are a lot cheaper (but you only get USB 3.0):
http://www.newegg.com/Product/Product.aspx...N82E16817392036I'm guessing portability isn't an issue, but my absolute fave little portable HD right now is the Hitachi Touro. Yes - violated my own rule against pre-assembled drives, but I've gotten these on sale for $79 at Staples, and they work off one USB port not two (like a lot of 2.5" drives without their own power bricks - you have to read the fine print!) and are fast and reliable.
http://www.newegg.com/Product/Product.aspx...N82E16822145597 OR
http://www.amazon.com/HGST-Touro-Mobile-Ex...s=Hitachi+TouroI don't know what capacity drive you're looking for - I have noticed that there are 2TB drives out there that don't cost much more than 1TB drives. If you do go the route of buying the drive and the enclosure separately, read lots of reviews - NewEgg and Amazon are both good sources, and make sure that the enclosure you buy is rated for the size and speed of the drive you choose. (There are some enclosures, for instance, that say they can only take up to 1TB - I'd avoid those, again - for forward compatibility, even if you're not planning on putting anything larger in the enclosure to begin with).
Assembling your own HD is dead easy, by the way. Generally all you will need is a small Philips screwdriver.