Get rid of them as you have determined that you don't need them. If I were you I would keep them all.
Originally Posted by rawhead
1. The Pentax is the only true spotmeter of the bunch so it would work as the spotmeter.
2. The Minolta is a great incident meter and it can measure flash too.
3. The Gossen can measure very low light, can be good for low light situation as well as for darkroom work.
I also use the light meter to measure light not just for exposure.
with that said, I actually have very good result using the a cheap digital camera (coolpix 5000) to do test shot and it works for both flash and ambient light and mixed light.