you can't tell from the preview when dealing with emitters... particularly if you have any SSS surfaces, the preview will be very bright and pixelated in those areas. The only reliable way I have been able to get a good render is to render a small image to at least level 10... at that point the output is pretty close to the final. Note, there are certain iterations which seem oddly out of sorts with the preview... I think it's 7 where everything goes quite dark...but the preview doesn't change... then by 11 it's brightening up... by 14 you should have a pretty clear example of the final. Once you get an approximate level then set the final render with that exposure, then, at level 10, compare the preview with the display again... and make adjustments... then again at 14, etc.
So, the lights in your example shoud be visible by 15 but they wont be as bright (most likely) as the in the preview... In other words, use the quick render NOT the preview to get an idea of your emitter levels. I had that problem getting the SSS right on my austin mini tail lights.
http://www.iandavis.ws/maxwell/mini_rear.jpg
Eventually I just ignored the odd glows that showed up in the preview and trusted 2 hour test renders instead... sucks if your on a tight deadline, but after a few times you will get the idea of how the two connect, then you can make better exposure guesses. good luck.
quirks in the beta I'm guessing
btw nice model, I can't wait for you to post the finished product in the gallery