The crowbar is already quite strong. Make it more powerful and you'd never have any reason to bother with a single-use knife.
I feel it's quite underpowerd, especial in the push reason. The damage increase could only be slight say take one less hit to kill.
Oh, another reason I dislike the idea is because people will be paranoid of people holding crowbars.
Just adds more flavour.
Neat, but seems more combat oriented than stealth and betrayal oriented. It also doesn't seem that useful.
Don't crowbar hits have a relativity low hearing range?