The Catz system is virtually identical to the Bellof which leads me to believe they share the same supplier. The difference between the two is themake of the ballasts. Bellof uses Philips while Catz has their own... not sure who makes it. I'm guessing Panasonic, but that's just a guess.

Bellof systems are considered to be the measuring stick in the industry. Very high quality stuff. I think the high cost is because of the reputation. As mentioned the bulbs in the Catz kit appears to be identical to the ones in the Bellof kit. If you look hard enough, you can find the Catz kit online for $450 and up. I'm sitting on a set... haven't gotten around to installing them because it's necessary to free up some space (airbox) for the ideal installation.

As for making custom head lights... This was to be a project I was hoping to tackle eventually when the financial picture gets better... but what the hell, I'll share. If you know how to mold plastic and have access to CAD/CAM equiptment, it is possible to mold a new inner housing that works with the stock clear lens (horn lights and all) to make a quad lamp projector system. Hella makes a set 75mm (I think that's what they are) projector lamps in high and low beams. These are the same ones used in the Saleen S7 supercar. Projector lamps are much better with HID conversions since the cutoffs are much sharper and controlled. Single beam HID conversions are also a lot cheaper. The quad beam look would be very nice I think. See www.rallylights.com about these projector lamps. There may even be an HID version for the low beam... I don't remember.