If you have never had a Boxster before consider reading "thinking of buying a Boxster" in the 986 forum. Lots to read there.
I have had a '99 Miata and then went on to a 2001 Boxster base. The latter is so much more car than a Miata. Have had the Box 2.5 years and would have bought a 2007 Cayman if my wife had said yes but she said no instead. Man card gone!
Did not consider the BMW z3 or z4. My Box has great air cond. and heated seats.
Just love it but may not be my last Porsche. Do look at other Boxsters as you can get a feel for what is normal in terms of sounds. Turn ignition on and make sure all lites light up especially the CEL one. Of course PPI is a must. And the requisite pics when you have made you choice. Enjoy the ride....
Check service history, accidents etc?