Next traffic source recommendation, please

[k@rnivore]

I am looking for a new pop/redirect traffic source to scale my campaigns.
I am already using:
PropellerAds, Ad-Maven, Zeropark, Ad-Cash, PopAds, Advertizer

I don't want to open too many accounts at once, since I am already spreading my budget over so many sources, so if you could recommend me just one more what would it be? (must be mainstream, I do not run adult yet)

I am trying to decide between:
TONIC, RTX, Self-advertizer, Clickadu (more suggestions welcome).