RE: Spyders -- There are two on Ebay right now asking ~$51 and $53k, and a similar one that was listed for $53 sold for 'Best Offer'. A few weeks ago one was listed by a dealer for $49k.
Porsche Boxster Spyder | eBay
I'd guess there are enough on the market right now that you should be able to find a private party in the high forties, obviously dependent on mileage/options. The release of the new Spyder is likely driving them down a bit as well.
(adding pic as description doesn't show price)