I just noticed on TireRack.com that the Firestone Destination LE2 is available in 235/55/20. I had them on my last vehicle (in 245/55/19) and really liked them - reasonably quite and comfortable, very good wet performance and decent snow traction (not as good as dedicated snow tires but better than any other all-season tire I've used).
$75 cheaper per tire than the Michelin Latitude Tour HPs that are the OEM tires.