I've always been skeptical of chiropractors. I tried to go to one and my cluster headaches got worse. I think one of the worst ones ever was right after an adjustment.
Like you, I'd rather not do any preventative meds. I don't like how sluggish the calcium channel blockers make me feel, but they do stop the cluster cycles (I get them in cycles, every few years). My neurologist will only fill up to 25 days worth of Fioricet at a time (50 pills). The problem is that I have several attacks a day, and because I'm limited to two pills a day, I have to suffer through the pain at times, so I don't run out of pain meds. In my case, due to the frequency of the attacks, it's most important to prevent the headaches, rather than treat them once I get them. In the interim, Fiorcet stops the pain pretty much immediately.
After reading that link I'm very interested in trying magnesium. It's interesting because they mention Raynaudís Syndrome as a sign of mag deficiency, which I do have.