I DIY'd 4 Cree Q5 LEDs into an aluminum casing with a dual spot and dual flood. I get 4+ hours on a 4400 mAh 14.8V Li-ion pack. It's brighter than the 13W HID system it replaced, but at least I can dim it down to a reasonable level. I have found that unless I'm on a long fire road, a 10W helmet mount does the trick on most trails. One of the sweetest DIY lightsets I've seen is
here. It's an epic thread, but the result is a cheap, very effective setup that can be custom built to suit your needs.