I am replacing my beloved 2007 997 C4S cab with a GTS. It seems most websites like edmunds and KBB underprice exceptional Porsche's based on selling prices I see. Anyone have a good site for a estimate?

 

I'm on the buying side and you are 100% right. I lost out on a couple of deals as a result of it. I ended up building my own database (complete with graphs) from the forum marketplaces, Autotrader, Craigslist, BaT, Cars.com, etc to really understand the market.

 

Heres one data point. I recently (last month) bought a 1 owner, CPO, 2011 Carrera GTS Cab PDK in GT Silver Metallic with 7964 miles for $73000. I thought it was a good deal since the 6 year maintenance schedule has been done as a part of the CPO certification and I get 4 brand new tires. Not to mention the 2 year/50k miles warranty. Here is the spec sheet -> https://i.imgur.com/fYlMWoO.png.