I've got a Kala KA-T (you can find them for right at $100) and it's not a bad starter instrument. Can't really compare it to any of the others but I think it sounds alright for the price - as a guitarist, I'm astounded that I spent only a $100 for an instrument that sounds as good as it does. You can hear it in my You Tube videos.
That being said, within a few weeks, I'd already started wishing I'd spent more and gotten a better uke. The KA-T is definitely a starter instrument. I've played a few ukes in the $250-500 range and there is a considerable difference. Out of what I've played (which isn't much), I really like the Mainland ukes - they seem like a great value, even though they're a good bit more than your starting price range.
If you are fairly sure you're going to really play, I'd follow the advice of others upthread and spend a little more. You won't regret it, and you'll end up with an instrument that will hold its value a little better even if you don't stick with it and need to sell it in the future.