Selling Domains

I own a number of different domains and am thinking about selling one of them (www.wincap.com). I recently received an unsolicited offer for the domain and so am pondering making a more concerted effort to sell it. There are a number of companies claiming that they can do the best job with this including afternic, Domain Name Aftermarket and Sedo. The domain is currently listed at Sedo for convenience, but I need to decided which of these, if any, I use. The annoyance is that all but Sedo require an upfront investment to even list the domain. This is frustrating because you pay regardless of whether the domain sells and then charge more money if the domain does sell. Who knows, I am going to keep pondering.