You can get a 2000-2001 maxima at a good price or even an 02-03 altima (4cyl.) with low mileage for >15k. Also you will be able to find altimas with transferable factory warranties. My friend bought a 2003 sentra SE-R spec-V and got the 100k warranty transfered to him from a private seller.
P.S. Don't sell the Z. I put mine for sale but when it came down to it I couldn't let it go.