If you're trying to put H3 HID bulb in the original projectors, you're going to have a bad time.
You don't even need the mounting brackets to change the shitty halogen projectors out for something decent. Just chop the original ones (I've done this). I also got the metal brackets from Lightwerkz, they were a pretty penny. I reckon you could get some locally cut for cheaper.
The Koito bi-LED is an excellent unit, only one I'd consider (or the low-beam only units, I have a bunch to try out). The Morimoto M-LED v2 looks good but haven't seen in person so can't say, but might suffer from strong foreground like most LED units. You are correct about the cooling GTSBoy, the housing isn't large. You could get away with some sort of one-way valve/vent. Otherwise, tried and tested D2S is the way.
I really should get around to experimenting with headlights again, have a bunch of OE LEDs and HID units to try out...