Hi John,
IMO you can very successfully use Ha for Lum, but for emission nebulae only. It would not work very well with galaxies.
Money permitting I suggest getting a 5nm Ha Astrodon - you will love it when imaging emission nebulae and won't be thinking in the future:
should have I gotten something else?
My second choice would be a 6nm Astronomik. In a heavily light polluted site, wider bandwidth will result in a lower SNR, so I would not recommend a wider bandwidth, if you want the best possible data.
Hope it helps a bit
