I wear a half-helmet, and the best earplug compromise I've found with wind reduction and being able to hear the stereo are the Hocks Noise Breakers, or the Alpine MotoSafe earplugs. Neither are real cheap, but the Hocks are cheaper than the MotoSafe. One advantage on the MotoSafe is you can adjust the amount of noise blocked by changing a small insert in them.
Both of these reduce the wind noise, but still be able to hear traffic and stereo.
YOu might check out earplugsuperstore.com for several optons on earplugs for motorcycles. I've bought several pairs from them, and have received very prompt service.