Mike,
Just to clarify there are a lot more than just those two differences you spoke of. The 2000 has 64MB flash rom vs 16MB on the 650. The 2000 can record 16 bit audio which can then be loaded into a computer and either burned on a CD or sent via email to someone or uploaded to youtube. The 2000 has stereo inputs and outputs, the 650 has one shared headphone/stereo output. The 2000 has a mixer to edit all the volumes, effects, etc. the 650 just allows to turn on and off tracks and doesn't allow for microscope editing of song and style data which the 2000 does.