From what I've seen, most companies are labeling their equipment "keyboard" or "synthesizer" simply based on if it has onboard speakers or not - which I could care less on.
The korg is actually pretty awesome, was around 400 bucks. It's just too small to be a primary instrument - but it has made a world of difference than the casio-only keyboardist they had before, hehe. But yeah, the Casio is... yuck. It sounds cheezy. It is cheezy. The voices aren't that fantastic and the options are just so limited on the thing. Plus, I really have no control over the sound unlike the mini-korg.
As per upgrading, I agree - I don't need something like a MOTIF or a complete work-station, but I would like something thats going to perform well on stage even once my skills are more advanced. I know even if I get a great learner board, its still gunna cost me 300-500 dollars, I'd rather throw in the few extra hundred and have something that will last me that I wont, a year down the road (or less) say "No no, I need to upgrade so I can do THIS". Keyboards are quite frankly expensive as crap. Golden crap. Laced with diamonds.
I'm expecting a hefty kick in the wallet, but I agree, I don't want to go WAY overboard. But like I said, if I'm spending hundreds I'd rather go the extra 50 yards and get more bang (and more importantly, more life) for my buck.