Thanka rikkisbears, you've been very helpful. I was aware about the MIDI in/out, and I will inquire on the Yahoo DGX board. Anyhow, it looks like I will be waiting til June for the weighted key version (YPG625), so I'll have plenty of time to check out the ES4 and some GEMs.
Too bad I won't be able to add a vocal to the headset out.

Can't have everything, I guess.
Took another trip to GC. I'll post about that elsewhere.
L8R,
Rick