stiffer mounts won't harm the engine.
if you are getting wheel hop that is bad very bad if you have a MTX you are gonna snap a tooth off the diff and then say good bye to the rest of the tranny. I've never heard of mounts helping wheel hop however tires, suspension, LSD and how you let the clutch out help get rid of wheel hop. if you feather the clutch out you will get less wheel hop and keep the RPMs under 2k to keep the tranny in 1 piece.

2003 Subaru WRX some mods Even if you don't have the answer, you certainly have to admire the problem. aka ZetecRacing