If you're going to do the suspension then you might as well go ahead and get it polybushed if you can afford to do it. Polyurethane bushes will last longer than the standard rubber items, so if you want to sort the suspension then it would be a good idea to do as much as possible in one go. The polyurethane bushes will firm the ride up a bit as well, so if you want to do it then go for it!
anti roll bar bushes do help on my old mk2 i replaced the anti rol lbar bushes front and back and there was quite a difference compared to rubber. the car didnt really have any other mods such as lowering.