Hi Dom,
I would seriously consider polybushing your wishbones - in fact I'm of the opinion that you only need to do the large rear bush as the fronts are not subject to the torsional forces that the back ones get battered with.
Your handling will become much more responsive and you'll have less dive on braking and less lift on hard launches/gear drop accelleration
If I were to do it again I'd have gone for this kit -
http://shop.grahamgoode.com/whitelin...28-68766-p.asp
The reason why I would opt for this kit is because you wouldn't need to retain the casing of the original bush meaning you can chop right through it with an angle grinder which makes the job much less of a b*stard!
When I fit my purple Powerflex ones it was bad enough getting the old bushes off and retaining the casing but also pressing the polybush in was a nightmare too... One is mangled and one is perfect haha...
So yes, the above kit will cover some aspects of your handling.
As for pushing harder you're better off with a Gripper diff, I've heard that the Quaife ones are sh*t in comparison -
I saw a vid of Tim Williams fitting one to a gearbox the other week and I'd take his word for it!
Also experimenting with a slightly lower tyre pressure should yield good results, for me on my 17's 32-3psi is best for handling.
Hope this helps!