Hi mate, firstly thanks a lot! It's a great tune to play.
I use a PJB Bass Buddy, so I have my bass, and a line from my iMac going into the Aux in, so I hear the track and myself. I then run the Line Out (which only takes the Bass input and not the Aux) and run that into the Line In on a Lexicon Alpha. It's not the best interface in the world, but it's cheap and cheerful and gets the job done. That is a USB interface so no power required, it just runs direct into the Mac. I record in Logic, add a bit of whatever I fancy with the plugins (EQ/Compresson/what have you). Then I just bounce the tracks into one stereo track, and align it with the video thats been recording the whole time. Export to YouTube and it's done.
There's probably better interfaces out there for not much more money (I'm dying for an Apogee Duet but they're SOOO pricey) but for now this does the job pretty well with no hassle
Cheers, hope that helps
James