What do I gain by going to 'performance' front end parts?

Except if you use a poly lower control arm bushing there is nothing to hold the lCA located on the pin besides the torsion bar. There has been an ongoing debate over the suitability of poly in LCA bushings for years. It has to do with the fact that poly bushings don't have any "grip" on the lca pin or the outer bushing shell the way that the rubber bushings do. Some creative individuals have found creative solutions to this issues, but rubber works for me.

I would go with rubber bushings and other strength enhancing mods like k-member reinforcements and subframe connectors. I have the poly bushed RMS upper arms and they do squeak something fierce. There are 2 different thicknesses of strut rod bushings make sure to get the correct one.

Have you already bought the QA1's? Bilstein makes a real good shock and is likely cheaper than qa1. Do you have swaybars? Larger torsion bars? Larger rims and lower profile tires? These are things that will improve handling and response without the tradeoffs involved with poly.