If you want a standalone dance machine that does basses, leads, and beats reasonably well and can't afford the 505, go the 303.

A sequential VS will give good sounds and realtime control from the joystick, (Personnally loved the Yamaha SY 22 because of it's sounds and vector!), but as far as I know it doesn't have a sequencer onboard, and is an older piece of gear so availabaility and reliability may be problems.

Prof