I know in context it's a terrible response, but I do the full Geddy and have an old Motif6 and an Alesis Ion. The thing that best gives you synth and string sounds is a synth. There are lots of cheap ones out there that you can plug right into your PA.
W&T, Carvin, Elrick, and Fender Jazz basses
Bongo #54, Carvin #80, Fretless #295, Elrick #40