Recently rode shotgun on an A320 with a crew (read: captain whose FO didn't question him) that seemed to think accelerating through building cumulonimbus clouds and the accompanying moderate turbulence was a good idea. I witnessed upwards of 300 knots being set and the standard hold speed was apparently 270 knots (who knew?). As I wasn't exactly in a position to criticize (being a freeloader and all), I kept my mouth shut and quietly pondered existence and my place in it.

So, question is: What's the recommended turbulence penetration speed for the A320 (and all its family members, if it's different)?