I've still got a couple of my specially designed front engine mounts sitting in the garage.
Solid front motor mount made out of Ultra-high-molecular-weight polyethylene with a grade 8 bolt.
My experience has been that there is a very small rpm range you will actually notice a resonance, and it'* at the very bottom of a gear when slowly accelerating. Nothing that has made me regret putting one on. This could probably be defeated by using some type of insulation between the mount, I've just got it solid on the bottom and an old chunk of tire on top.