"Having an arranger gives you the best of all worlds IMO."

I agree - for expensive arrangers.

I would love to recommend any Ensoniq synth (especially the SD1) to you, but I recently had to retire my SD1 as it had become unreliable; I only kept it going this long due to monthly TLC; the control sliders are especially fragile. My problem now is random detuning; I think its a power supply issue but I don't have time to check!

The Roland XP series have a good reputation and are well-built. Ditto almost anything from the Korg Triton line. Yamaha Motif's are also good but I don't know if you can get one in your budget. The Alesis stuff also looks useful but I haven't ever played one.

Hope this helps!