sorry to hear the other deal didn't work out bud. thats crazy that they called you last minute like that, I would have them reimburse me for gas or something
As for the 3 new prospects I would go with either the 09 nismo or 10' sp. The black nismo is almost the same price as the white, but with almost 6k more, so that is out, unless you really like black.
Between the white nismo and white sport I would say you would have more bargaining power with the 09 nismo, as it is older, more miles. However, the base/sport is a year newer, and it has the warranty left over (if that is important to you). So I would say it boils down to who gives you the better OTD price. Either way with the 20k check plus 10 cash you should be walking away with one of the cars, unless they both sell.