Are the Audio Technica ATH-M50s a good first pair of headphones for a beginner audiophile?

Yeah, they're supposed to be great headphones. Just make sure you listen to them before buying. If I were you I'd also listen to the Sennheiser HD 25-1 II. They're also a great sounding headphone, but they might be a bit more suitable for DJing. Whichever phones you get, I'm sure you'll love 'em.