Best thing I ever did for my VP V6 was a 5 speed (which you already have) and a 3.7 ratio lsd. Those are the only mods it's really got it's no race car but it's pretty punchy for a V6. Maybe with a good air intake, extractors and a tune it would go even better.
On the other hand if you're going to start spending more than the above I would say forced induction is the way to go. You could spend just as much on an N/A for half the power of a good turbo 6. And those good old Buick steel blocks can take a bit of boost if it's a nice healthy engine.
So yeah I say either do a little and be happy with what you have or if you wanna go all out look at some turbo options.