AdsDaq - I would stay away from this one, for this reason: AdsDaq Review
AdBrite - Professional, reliable, but as you mentioned: Low earnings in some niches.
Smowtion - Pretty low earnings overall. I earn less with them than I do with any other network.
AdSense - A good network if you don't mind having to constantly be on edge for fear of them just taking your money and banning you without a reason.
I would follow the recommendations of Will and check out:
- Direct Media Exchange (I am looking into this one now, but can't figure out how to sign up. :S)
- Tribal Fusion
- Burst Media
- Ad Dynamix
I think you should try Smowtion. I like it the best.:)