Consider the Spectrum Synth either a poor man's Nord Lead or a digital Oberheim Matrix. It's an affordable simulation of an analogue synthezizer module that uses Sampled waveforms and digital envelopes and filters to create close approximations of analogue sounds. It comes with 256 presets. The first 64 patch locations can hold user created patches. The Peavey PC1600 MIDI fader box can be used to program the unit like an analogue synth. I like it because it does a good job at approximating analog sounds. Because it uses an analogue approach to programming, it's much easier for me to understand how to program it than most recent digital synths. It cannot be programmed with out a PC1600 or computer editing package, so you may want to factor that into your purchase.
Comments About the Sounds:
(Thanks to David Johnson for this info.)
and Bobo Wieland for the pic