In regards to the H13 HID kit retrofit:
You will not like the results of the H13 bulb conversion in a DOT spec reflector housing. The H13 bulb is a dual filament bulb that is relatively short and stubby (compared to 9007 or H4 bulbs).
If you used a stock headlamp reflector with an HID H2S bulb that was rebased for the H13 setup, the base would have to be thickened quite a bit to literally move the bulb back so that the "filament arc" of the HID bulb would match where the low beam filament position would be in a standard halogen bulb.
Also, the H13 bulb (similar to the 9007 bulb) is a stacked and offset filament bulb as well. This means that you have focus points that are different than a standard Z-axis aligned bulb (like the H4, 9006, and others).
If you did attempt a HID retrofit with stock reflectors, you'd end up with a huge hot spot that's off center.
So, your best bet for any headlight upgrades for the H3 will be:
-Brighter bulbs
-Reflector replacements to european code reflectors (usually an H4 bulb is used to do this, which means a rewiring job as well)
-Reflector replacements to european code reflectors AND an H4 HID upgrade
-Projector HID's (this is the way to go!).
To answer the question about HID's and losing high beams. No big deal. HID's are 3x as bright (as long as you use a 4300 to 5000k bulb) as any halogen out there. Road bounce of the light alone will provide you with enough light to brighten signs 1 mile away. I have HID low beam only on my H1, and I have not lamented the loss of high beams.
As for blue color bulbs - they actually produce less effective light than clear bulbs. A great chart would be one that's found on this link:
http://www.azhog.org/headlights/Hell...visionplus.htm
Towards the bottom, you'll see a chart of effective lumens vs. kelvin color temp of the bulb. The bluer the bulb, the lower effective light you actually end up with. In some cases, a overwattage 80w headlight bulb will produce more light than a HID 10000k bulb because of the inefficiencies brought in by the filtering/adding of the blue in the glass.
I haven't measured whether the H3's reflector is a 7" or 5". If it's either, I can give the "plans" for a retrofit kit in either reflector or projector format to HID. It's essentially duplicating what others have done. If it's 7", it's been done before on H1's and H2's. If it's 5", you can follow what was done before and match it to the H3's specific wiring needs.
-Steve