I have used Modulus, Momentum, Fresco , AfterBurner2, and Lumiere. However, Tachyon was styled specifically for JomSocial. However, I would not let any of those affect me decision. It depends greatly on what the look and feel you or your client is wishing to achieve. Jomsocial will function within any of them. Some minor style overrides may need to be created but Jomsocial 3 blends well with pretty much any theme.