Sony's just amped up its Walkman line with the WH series of headphones, though the term "headphone" fails to capture the essence of the new models. The company's also stuffed a 16GB MP3 player into the high-end NWZ-WH505 and a 4GB unit into the NWZ-WH303, giving you up to 4,000 tracks without any other device. It's also compatible with a Mac, PC and other playback devices v
