I would like to trade in my Porsche Boxster 2001, for a Maserati Spider.I am willing to pay a reasonable price difference in cash

I think the best alternative is; to negotiate on asking price of Spider. And, you could come out better with; more pocket spending and a reasonable trade. Estimate the, appraisal value on: EDMOUND'S.com Website before you trade to; be accurate with the true value of the Car. Print the trade value for, yourself for tax purposes This tool, is Always wise before; trading to Private owners. Garaged cars tend to; hold more Appraisal/Loan value then average wear and tear vehicle's.