The impact of an $8,000 first-time homebuyer tax credit is being felt most right now in low-priced markets. Ones with healthy economies, outside former bubble areas, are seeing the best home-price gains. Areas hit hard by foreclosures might have preferred the boost. But instead it was the Cumberland, Md., Davenport, Iowa, and Oklahoma City metro areas that posted the top existing-home price rises in Q3 from a year ago, according to National