I have 5tb's worth of western digital elements ehdd's. Not obtrusive looking at all, and have had them for years, don't make a noise and are really quick to load up and transfer files to and from
Seeing as your into djing though, I'd reccomended keeping your set on your main drive for the night, with a backup on the external hard drive, along with the rest of your mp3's
I wouldn't want to risk having my main music program's read only from the external one as the read and write speeds via USB are limited compared to a built in hdd, which will affect performance