I saw in the factory manual there was a HID option for the Highbeam.
Is that for the Subaru or KRS? AFAIK
the KRS factory manual makes no mention anything but halogen lamps.
I can't remember where, but I ran into a thread where someone made baffles to redirect light from an LED. Obviously that's not a choice with an HID. In fact, I think getting an HID in the right spot to get the optics of the headlight (reflector, baffle, lens) right is pretty much slim to none. Having had to seriously modify the high beam socket to make an HID, I'm almost certain the light-emitting spot in the lamp is most likely anywhere except were is should be.So, bottom line, the trick is to find the brightest halogen light possible. The loose end here is whether the extra heat will cause problems with the reflector or rest of the headlight. I simply don't know the answer.
Two points about wiring. The original ground wire (brown) from the headlight is under-sized and the connections are poorly made. It won't matter how good the wiring to the light is if the ground isn't to the at least the same spec, and actually should be up a point in size from the supply lines. The existing ground point should be a direct chassis ground. Keep the wire short. clean the mounting point fully, and smear di-electric grease (get it from the usual car part stores), and then make a tight connection. The grease will seal the connection and will be pressed out of the actual contact point.
A 55W lamp pulls a touch over 5A (55 watts divided by 12.4 volts - Ohm's Law). A 100W lamp approximately doubles that. The high/low switch isn't intended to carry that load. The existing wiring isn't designed to carry that load. The fix is to install a relay, controlled by existing wiring, controlling new, heavier wiring for the headlight. (there are plenty threads about the details).
Although an LED lamp, replacing the low beam H7, improving the wiring won't hurt; it'll remove what small amount of voltage drop exists (lamp current times circuit resistance equals the voltage lost - Ohm's Law again). For the LED, that drop won't be a major problem, but, since the high beam wiring must be improved, might as well do the low beam, too. If a halogen H7 has to go back in, it'll benefit from the new wiring. But about the high beam, now drawing 10A. Going back to Ohm's Law, double the current and that doubles the voltage loss. And voltage loss means a dimmer headlight.
OK, I hope everyone paid attention, tommorow there'll be a quiz on this.