6H30 Tubes

Everyone says the sound of these tubes can’t really be changed, yet there are cheap as well as very expensive versions available. I use these in an AR preamp. Aside from matching the tubes, can I get a better/different sound going to a more expensive tube? My current tubes came from Upscale Audio and if I recall were well under $100 each, maybe even the pair. I know there's threads on these here, but maybe there's updates on what folks have tried.