I had the lenses in my headlights replaced. The housings are the original ones but the lenses had come loose and were crumbling at the edges. I need to fix the picture links but here's my thread on the upgrade:
https://www.subaru-svx.net/forum/showthread.php?t=59777
A full retrofit should be doable by any experienced headlight modifier, but if your hardware is in good shape an HID kit will get you most of the improvement.