I have the set of AEM pulleys. They don't do a whole lot, but they may help the bottom end a little.
The AEM set is a "safer" way to go. It just deals with the power steering and alternator pulleys. The UR changes the crank pulley, and I don't believe that it incorporates a harmonic balancer (Someone verify this? There has been contraversy about that). The UR set gains much more power than the AEM set though.
If you really just have a CAI, I'd recommend getting an exhaust next. The gains will be much better. I have just a CAI and pulleys, and I'd rather have an exhaust.
