Very cool! The dash swap is definitely way more involved in a BD than a GC (lots of firewall mods) which is why I kept the Legacy dash & HVAC but swapped *everything* else. It was a lot more wiring than a regular harness merge, but I'm very happy with the results.
Doing all the bushings & motor mounts will definitely wake the car up. If you're going to lower it & replace the ball joints anyway it you should check out the whiteline roll center adjustment kit. 04/05 STi steering rack is a great upgrade too!