If it has to be an allrounder: Roland XP-30. If it doesn't need to have keys: Roland JV1080 or 2080. If You want to have analogue feeling, what about a Roland JP-8000, Clavia Nordlead, Oberheim (Viscount) OB-12?
Or a JD-800. No allrounder, just an easy to program digital synth.
No, I'm not working for Roland .
BUT: for 750 USD You will only get such a professional instrument second hand.