I don't think Bose was available yet for 1995 Silverado's. At least I've never seen them.
You will get sound out of the RE Audio speakers, with the factory head unit, but it won't be much better than the factory speakers. The sound quality will be slightly better but it won't get louder. They may even require more volume compared to the factory speakers. Whatever you do, do not drive the volume up to the point of distortion. You will kill your shiny new speakers.
A new aftermarket head unit will help, watt per channel wise, but it's not much more than the factory head unit.
I agree with SCOTTYINWV, adding an amp with high level inputs, would be best for powering the RE's.
You can run RCA cables to the amp when you get a new aftermarket head unit.