If you're a metal fan and a King's X fan, Galactic Cowboys will be right up your alley.
As for influence on grunge:
1) Jeff Ament said they "invented grunge."
2) After Sap, Jerry Cantrell was asked when the next AIC album would start and he said, "I'm not sure. We're waiting for the new King's X record to come out first." They laughed a bit and Cantrell mentioned how most of the riffs on Facelift were mutations of King's X songs or melodies (They are - listen to Facelift back to back with Faith, Hope, Love, and the self-titled album. It's shameless).
3) One of the DeLeo brothers (STP) - can't remember which one - once said "Grunge was born in Katy, Texas (Ty's hometown).
4) Soundgarden used to reference Ty and Dug in interviews all the time in the early 90's as an influence.
The other influences are a bit odd - bands that have been around forever have even changed their sound on one or two albums, citing the King's X influence (Queensryche's Hear In The Now Frontier, and Kiss' Psycho Circus - both DeGarmo and Kulick admit to being huge fans). Jon Corabi brought some KX influence into the self-titled Motley Crue album he sang/played on. You can also frequently hear Ty's influence from Reb Beach on recent Winger and Whitesnake outputs, as well as on George Lynch on Dokken's Shadowlife.
I could go on and on...