I have the Ketron SD2 and it's a gem. If you can find a used Roland JV1010 or equivalent or even the external soundcanvas that's not bad either. There is a dare to compare with sounds of different synths here on the pg website.

Be aware that if you plan to use both a synth and Real sounds you need a mixer in the end. A cheap 4 input Behringher is around $50 to $60 bucks, with preamps and mics and a way to send the signal back into the computer for recording.

John Conley
Musica est vita