I think I'm with brett s, and if I were to buy new wheels I'd go with 225/55 on 17x7. This will provide 0.4" more width and 2.4% higher speed at the same rpm. It will also lower the ratio of tire width to wheel width from about 1.3 to 1.26, which is supposed to help a bit.
But staying with the lighter weight (and free!) 16" wheel may be the way to go for me. Like brett s, I think I'd lean towards 225x60, but might consider 225x55.
From what I've gathered, though, a good high performance tire, even of the same specs as the Yoko OEM, would make a big difference. I like the reports on the Conti Extreme Contact.