Well, Merge isn't currently accepting new US sign ups. There are rumors that they will start very soon, but there have been similar rumors that turned out false since they blocked US players.
As stated above, if you decide on Cake look at a skin like Intertops that processes their own Cashouts or you may find yourself in a race to see who pays first, FT or Cake
Minted Poker, True Poker, and Bodog are all solid choices. They each have some positives and negatives. For example, out of these three Bodog has the most traffic but they do not have Rakeback and there is a 4 table max(sounds like not an issue on the 4 table max for you).