Curious, is that a new bike? It looks new and "made in China" sticker would lead me to think it must be fairly recent, but the current Bikes Direct version of that bike lists and shows dual caliper brakes.

Like f4rrest, I would look to replace those with a dual pivot. You may still wish to upgrade the pads, in which case the Koolstop "Dura" type is typical replacement for shimano style brakes and will work for most Tektro and Nashbar calipers.

The amount of tire clearance in your pictures makes me wonder if you might need a longer reach brake. I would measure first, scroll down here: Installing and Adjusting Caliper Brakes to the section titles "Reach".