Thanks for the very informative reply! I have a set of OEM 18s for winter, so I should be OK. I'm a little curious why you mentioned that I may get tired of the 214s. Would the ride quality be too harsh? Would they hydroplane easily? I guess I'm trying to figure out the drawbacks of style 214s.

I'd only get 214s if the trade with my coworker goes through. Otherwise, I'll hold onto the 334s. For the time being, I'm perfectly happy with the traction I get from my 334s. The M3 gets really sticky track tires