My advice to anyone that asks this question is, "Try them all, and pick the one that works the best for you".
As for those you can trust, as pr0 says, usadialers are cool.. Also
http://www.dialerking.com ,
http://www.dialerheaven.com ,
http://adult.gibhar.com (run by Richard at AWI),
and of course, us.
There's many others too, but these are the ones I can say I consider trustworthy and worth a look.
Jason.
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