Solid Motor Mounts

My motor is stock and my mounts are shot. I'm looking at these but kinda weary cause I've heard some things about using these. Like it might mess up my stock K-member????? Ever hear of this?

I dont care about a little bit more vibration if it will make my car perform better.

I drive my car pretty hard on the street also. I just wanted to hear what you guys think about using these mounts on a pretty much stock set-up? Just shoot me some pro's and con's about these mounts.

Thanks