While I haven't necessarily tried products from this company, that fact that they give an address and telephone number is some promising evidence that it is a legitimate source. Most websites will not give any sort of specific location or contact info (except for maybe a bunk email address) if they are trying to con you out of some money. However, just because they may be a legitimate source does not mean they have good products. Another promising sign, though, is that they have an official listing in the yellow pages: http://www.yellowpagesgoesgreen.org/Makawao-HI/Alternative+Medicine I think it may be worth checking out and reporting back since their price for a pound of kava is relatively cheap.
Your last word is exactly what I'm worried about. Although Hawaiian kava seems to have one of the highest kavalactone contents there is (this does vary widely from producer to producer).
Well, the price is comprable to Bula Kava House, which has received glowing reviews by some of the members on here for their strains of kava. You may want to check them out if you're looking for a cheap, but effective kava. There's plenty of reviews on here for their products, including one especially good review by Vekta for BKH's Boroguru Kava: http://kavalounge.yuku.com/topic/386/BKH-Boroguru-Kava-Review.
After several emails & phone calls I canceled my order w/ Medicinal Herbs. The only herb they must be interested in selling is the kind you smoke. Don't waste your time w/ these idiots!