I've had a couple of mr2 (mk1 and mk2) and they are different cars to the 350z - the z is less sports car and more GT really.. much more comfortable/softer riding/quieter.. the dry handling in the mr2 was better but the wet handling in the z is a lot safer and there is more grip generally. personally I got shot of the mr2s after a few 6 hour stretches heading up north where my brain nearly imploded..
if you just want to replace/upgrade the mr2 then get a lotus though!
(and if you want a boring sedan then get the 5 series)..