Find help with the purchase of a Cayenne Turbo S, 6/2009 with approved warranty!!

Hello dear community, I am about to buy a Cayenne Turbo S. This is the following offer set in mobile.de: http://suchen.mobile.de/auto-inserat/porsche-cayenne-turbo-s-approved-garantie-bis-3-2016-karlsdorf-neuthard/203246789.html?&original=PARK&ticket=ST-1167846-AsHlcAbedktLGzhQZlP4-mycas46-2_c01_4201 The seller holds on to the price, does not drop a cent. On March 11, 2015, the vehicle has a new approved guarantee valid until March 11, 2016 (cost 1300.- Euro), which would of course be transferable to me. No defects have been detected on the vehicle. According to the list, the vehicle with special equipment has a new price of approx. 158000.- Euro (calculated with price list 2009), how do you find the selling price? Hope that someone can help me whether the vehicle is purely purchaseable from the recognizable data, or possibly overpriced is offered. Greeting Dixie