I haven't seen too many 20W (even 10W) sub-100 dollar lights either. Plenty of 1W LED headlights though.

I did the 20W halogen light from Home Depot, the Malibu spotlight. I can't tell if that's why you are looking at or not--darn work internet filters. I've been ok with the light as-is: I'm using the stock 20W bulb, which is not very directional at all. I suspect it'd be the ticket for offroad riding, as the large cone of light does work well at showing a large area. Problem is, it washes out with oncoming traffic, and there is a dark-ish spot in the center. I don't ride with a lot of traffic at night, so it hasn't been a problem. I did buy a 10W MR16, but just haven't bothered to swap it in to try yet. The bulbs are kinda pricey, at $7.29.

It's certainly worth trying for $12. I'm in the same scenario, I had some batteries already. The battery is pretty heavy, 7.5Ahr, must be like 8lb (someday I'll weigh it); but I'm pretty sure it'll work just fine for my sub-hour long bike rides. I also just carry the battery in a fannypack, so it's not weighing down the bike. I'm not sure what the light weighs, but it's not made with steel. Probably a pound.

[The wiring is a quick disconnect type of connector--Anderson Powerpole--so it shouldn't be a real problem in case of accident.]

Oh: I did post some pic's of my setup in the "Total Geek" sticky on this forum.