I'd recommend getting a hotswap drive enclosure and buying at least one extra tray for it. The reason for this is that installing a drive in such an enclosure is extremely easy and it gives you the capability of using one enclosure with multiple drives - e.g. one drive for your sample library, another for backup of your files. I have an enclosure sold by MacGurus
http://www.macgurus.com/productpages/sata/BurlyHotswap.phpDespite the name of the vendor, the enclosure is not Mac specific, however it is now listed as "out of stock," so if you are interested to find out when it will become available again, you should contact them. (They have an online inquiry form and are quick to respond). This enclosure costs $121.00. Extra drive trays are $20
A similar enclosure is available from Granite Digital http://www.granitedigital.com/catalog/pg47_hot-swapdrivessystems.htm
However, this enclosure is more expensive ($150) and the drive trays are $30.
A third possibility is the new FirmTek SeriTek/2EN2 enclosure which can hold two drives but can be used with just one drive installed. It costs $200. http://www.firmtek.com/seritek/seritek-2en2/
This enclosure as the advantage of having the new eSATA connectors on the housing. (The other two drives have the older SATA connector - - a connector not designed for frequent plugging and unplugging - - the rationale being that while you may swap drives in and out of the enclosure you don't need to unplug and plug the cable to the computer very often. Most newer SATA cards have eSATA connectors which means that, if you have a card with eSATA connectors and decide upon the MacGurus and Granite Digital enclosures, you would need a shielded SATA to eSATA cable.)
While the FirmTek SeriTek/2EN2 costs more than the other enclosures it comes with two trays so, for example the Granite Digital enclosure and one extra tray costs only $20 less than the FirmTek SeriTek/2EN2.
I hope this is helpful.