Bike recommendation?

Hi, can I please get an opinion on this Cannondale six13?

Seller is asking $400 fixed.

Details:

Cannondale Six13 54cm road bike. Frame is Aluminium and carbon fiber. Carbon fiber fork, seat post, and bars. Made in the USA around 2003-2004? Dura-ace group set (not sure about the cranks). Bottom bracket and cables done in the last year. Well maintained and kept indoors. Ridden frequently

Up grades: Fi’zi:k saddle, Rolf Vector Comp wheels and 25mm gatorskin tires with some good life in them yet.

Very light and fast, though it’s a joy to ride, I prefer an endurance road bike and am looking to upgrade. Tuned in August.