If you're worried about your top speed being a little lower than a road bike's, consider de-converting it to the original road bike. For me, street fixed is about ease of maneuverability in heavy traffic (and lots of red lights) as well as a low-maintainance, simple bike that won't cost too much to keep riding.

To put it shorter, I vote 40x15.

Of course, I don't think getting a new cog for your freehub will be very expensive, which is another way to adjust your gearing. You can probably find a used one as well. 52x20, maybe?