Bass ukes are cool, but at $600, you're way better off with a MIM Fender P bass or J bass (they even look better in my opinion). Or if you're looking acoustic, there are a lot of acoustic basses for half the price, that will sound much better. And the thing is, that acoustically, acoustic basses are pretty weak, and very soft. I own an Ibanez acoustic bass, and it pretty soft acoustically, and when you plug it in, there's massive chance of feedback because of it's big body. But you still need a bigger body to push those lows, so if my full sized acoustic bass doesn't cut it, a baritone uke body just won't cut it either. Compare the body size to the upright bass in the background of the video. (Thus, this uke is designed to be played plugged in...because acoustically it's not going to be good at all) So if you're going to have to play amplified anyway, My pick would be any electric bass in the $600 price range.
Then again if you're looking for another cool uke, then there is really no substitute.
But for my money, I'd go for a Fender P Bass. Plus, strings will be easier to find.