Have you thought about getting an HID kit? For the low beam you can pickup any H7 kit.
I've thought about HID and LED replacements as well as uprated halogens. I need to preface by saying, I'm a stickler for beam pattern and vertical cutoff on low beams. My blood pressure goes up whenever some yahoo in a jacked up pickup truck pulls up behind me, with 8000K purple HIDs bulbs in reflector/lenses that were never meant for them. Blinding and offering no meaningful improvement in down-the-road light. Ugh, no thanks. The problem is, at least if properly designed, lens/reflector combinations are designed to focus and distribute light from a certain focal point. Halogen bulbs emit light from a defined line-source - the filament. Dual beams like H4 have two filaments, one of which is shielded to prevent scattering of up-light on low beams. HID bulbs radiate light from a point-source sphere, not a filament line source. LEDs are even harder to engineer, since the light source is unidirectional, perpendicular to the plane of the LED emitter.
I'm open to any improvements but I really would like to see before-and-after photos and/or video of the beam patterns on wall and down the road. If you've had a good experience, please share!