I bought one of those stepstool/potty/toilet seat 3 in 1's (First Steps or something similar). It's great as a potty, very sturdy and you can just pull the bowl out to empty and rinse. It doesn't have any extra music etc. As a toilet seat without the bowl in it, the ring has quite a harsh edge, so I ended up buying a soft seat for toilet and we used in combination at first (potty in lounge), after about a week she just now uses only the toilet.

Oh, and we got the potty about a year ago for 'fun use', so I don't think it's a waste to have both.