Its your call guys ,but the Cats alone do not impeed power.The new cats built these days actually breath quite well.There is a slight back pressure that might add a bit of high rpm power,proably not more then a single hp ,but if it is in your case adding more by removing, then it will be at the expense of torque in the lower rpm's.Exhaust will be louder as the cat acts like a resonator also ,so removal and louder exhaust does not necessarly mean more power.
Then there's the emission issues which is another discussion elsewhere.