Whiteline Anti Lift Kit: Great, but illegal in all but prepared and Mod Autocross classes. So bad if you want to autocross.
Steering Rack Bushings: Great stuff. Senor cheap bastard says get the blue/purple ones for $5 or more less than the whiteline
Rear Subframe Lock Kit: Harsh feel and noise I think. Same as ALK as far as autocross classing. If you want to, you can do the urethane bushings for the front of the rear diff brackets. A few of us have those. But they also add noise.
STI trailing Arms: Not sure they add much value.
Lateral Link Set: Best way to give you rear track and camber adjustment if you need it.
Finally... Rear and or Front Endlinks (to pillowball or not to pillowball): Yes, and spherical bearing. Best rears IMHO are:
http://www.poltec.us/products/subaru...s/1a-df001.htm