I tried selling my 2004 S281-SC coupe with very little luck for the price I was asking ($38,000). I had it listed on Performance Auto Sport for 6 months with a lot of calls, but no good offers. Towards the end, I had the best offer of $34,000.
My car sounds pretty much like yours with the difference being mine is a coupe. I have all the Saleen upgrade options except the Maxi-Grip differential. I have 3,000 miles on it too.
That should give you a gauge...I asked Mark (PAS) his opinion on value and pricing and his advice was pretty much dead on to the offers I was receiving ($32,000 neighborhood). Yours being a convertible speedster should pull in more, but I don't know how much more.