Or simply use plugins build for the task. ReFX QuadraSID and Plogue Chipsounds to name but a few

There's something to be said for using proper hardware though. A sequencer can still be used for the sequencing part

Ooh didn't know about those plug-ins, are they compatible with most programs? Will have to give them a try.

They're VSTi's so yes, most DAW's will accept them (PC). I think there's a wrapper for OSX which will load PC VST's too...