7Search will convert if you manage the campaign properly, as will GoClick. FindWhat also. I just ran a brief test with Mamma with inconclusive results – $1 a click is fairly affordable but the money went a little too rapidly and no real money players yet. Gonna have to put some more money in there to come to a real conclusion.
Actually, I’d only rule out Search123 and Kanoodle completely from a list of the main second tier PPCs. I took over a PPC campaign for a major UK online casino about a year or so ago where their aim was to reduce costs as much as possible but keep the same number of new depositing players (they paid me 50% of the saving each month) and one of the first things I did was kill all Kanoodle advertising. Pretty much all the others they used (Overture, Espotting, AdWords, FindWhat, 7Search, GoClick, LookSmart) we got some ROI from.