Perhaps, perhaps not! The light on your helmet doesn't need to be as bright since that light will mainly focused on an area close to the front wheel, and the occasional flash through a drivers side window or a street sign. The bar light is intended to shine further distance thus should be the brightest of the two lights. I use a Cygolite MityCross 480 (480 lumens on high) on the medium setting for my helmet light and at that setting it puts out more then enough light for my needs at about 320 lumens. So it depends on how crazy you want to get, personally I would just get a ExpiliOn 400.

In case your wondering I use the Philips Saferide light on the bars, this light is fantastic, it may "only" put out 400 lumens but due to the aiming (low and flat like a car) of the beam is equal to 1000 lumen light. Run time on high is bit short at 2 hours but on low it will run for 8 hours. I usually run it only on low but occasionally on dark country roads with no moon, or raining I will crank it to high, but I rarely ride for more then 2 hours after dark anyways. Besides after the 2 hours on high it shuts down to low and will run for another hour. Batteries are readily available for it too since they use 4 AA rechargeable bats and not some dedicated pack. You would have to pay at least twice as much for a different light to get the same or more output then the Phillips. I consider the Phillips to be the sweet spot in lights, just the right amount of light without being an overkill at just the right price without taking you for everything you have, very much like the Cygolite ExpiliOn 700. The difference between those two lights is the ExpiliOn uses a flashlight type of beam, and the Phillips a car like beam which projects further without hitting drivers eyes.

If you want to wait for Christmas, save up a tad more and get the Phillips and then use your current ExpiliOn for the helmet.