Lowe's has a nice allen + roth sink w/ marble top for $349 (was $899).
Excellent reviews on this sink, with a 100% recommendation rate.
Some other sinks worth considering
Patmore Mocha Glaze 37-in Undermount Single Sink Bathroom Vanity with Granite Top - $399
SCOTT LIVING Canterbury White 36-in Single Sink Poplar Bathroom Vanity with Engineered Stone Top (Mirror Included) - $399
Style Selections Morriston Barn Door Farmhouse 30-in Undermount Single Sink Bathroom Vanity with Engineered Stone Top - $199