You could also take a look at the Casio Privia PX-330 for around $ 699
88 weighted keys, 250 tones, manual says it's General Midi compatible --16-parts multi-timbral.
midi in/out as well as USB connection -- and it has built-in speakers.

I've never used or heard this keyboard, but you could check out reviews at sweetwater.com
and musiciansfriend.com

links below:

http://www.priviapiano.com/products/PX-330

manual
http://support.casio.com/pdf/008/Web_PX330E1B.pdf

midi implementation
http://support.casio.com/pdf/008/PX330_MIDI_e_0910A.pdf

brochure
http://www.priviapiano.com/resource/PDF/PX330_Brochure_FINAL.pdf

http://www.sweetwater.com/store/detail/PX330/

good luck,

John