This is the appliance forum. I think you'd get better responses in the kitchen forum. :)

When we redid the counters this summer we replaced the standard island bar style sink and faucet with Kohler and are very pleased. Also went with an Acquia Pure full flow cold water filter on the cold tap to replace the separate filtered water spicket. The new sink takes the same counter footprint as the old top mount but provides WAY more sink space. The pullout faucet with stream/spray buttons is handier than I thought it would be and is easier to clean around than the old faucet. The 15x15 sink should fit as the specs state "18-inch minimum base cabinet width".

KOHLER K-7506-VS Purist Secondary Pullout, Vibrant Stainless

http://www.us.kohler.com/us/Strive-15-x-15-under-mount-bar-sink-with-basin-rack/productDetail/bar-sinks/941428.htm

http://www.amazon.com/3M-Aqua-Pure-Under-Filtration-System/dp/B00M216HFW#productDetails