Tires and Fluid, Pads, MC brace would all help braking/feel, in the order listed.
Tires are the first best thing for actual braking; fluid (DOT4) firms the pedal up,followed by pads which improve both feel and performance; a master cylinder brace is the last relatively easy thing that can be added to improve feel.
Additionally, from what I'm reading about subies, is that they have booster swaps that can help the overboosted feel (like in GM cars).
The STi or any monobloc caliper would also help feel since it flexes less than sliding caliper designs.
SS lines aren't really a good idea, since a possibility exists for catastrophic failure should grit (= abrasion) get between the SS outer layer and the teflon tubing inside. Consider that BMW uses rubber lines, last I heard.