If it ain't broke, don't fix it Luke!
I've seen many reports on here that agree exactly with what Tony said about polybushes. If you've got the spaceship polybushes, i'd say fit those and see how you get on driving on them - if you really want to tighten the front up more then perhaps consider the control arm to chassis bushes but unless yours are seriously worn, they won't make a lot of difference, even renewing with standard rubber and i suspect you may transfer an unacceptable level of vibration with stiffer poly bushes in them.