The function of engine mounts is to isolate the vibration that the engine produces from the chassis (and your butt).
Any "Performance" engine mounts will offer less isolation.
Upgrading to poly has some benefits:
-you can transfer more power more quickly to the ground
and some negatives:
-VERY Uncomfortable to 95% of people (most folks thought my car was terribly broke), but I in fact, enjoyed it.
I liked not having any slop at all between my engine and the tires.
The stiffer you go (you can even buy solid engine mounts) the more of each of those things you will have.
Green poly virtually negates use of an in-dash CD player.
A good compromise is usually replacing some with poly.
On the A2 chassis, you can replace the lower front with poly (or hockey puck!) and leave the upper front stock,
It will take up the slop in acceleration, while leaving the rest of the feel decent.
-Brad