Check these guys out:
http://www.expomc.com/
They all list as eBay auctions, but you can call directly, too. Reputable place with a lot in Houston. They're also a good price gauge for looking in your own area. They generally sell the cars for $500-$1000 below their listed "buy it now" price. I watched prices for about 6 months before I decided to buy my 2000 and I found that these guys weren't far off the fair price and their inventory is high quality so it's a good barometer for comparing good cars in your own neighborhood. They usually have a few Boxsters.