A couple things to keep in mind:

1. Lowering unsprung weight probably will not have a significant effect on lap times, but it could dramatically improve the suspension, increasing confidence, providing advantages over tracks with rough patches, etc. However, that said...

2. The shocks were valved and sprung for the stock Subaru parts. Changing the weight - higher OR LOWER - could also adversely affect handling. These things all work together and you can't change one without considering the effect on the others.

In the end I personally feel that unless you have an unlimited budget or just really, really want some cool uprights, performance/racing parts money is better spent elsewhere first.