Exhaust Help Needed

You don't need a whole new cat back system, you can just buy mufflers and have them installed into your existing system. You just need to make sure you get the inlet/exit size and offset correct. Also, a good shop can put flanges on the new mufflers you get as well as the ones you have so can can easily switch back and forth if you like your old ones better.

Removing the CATs means your car will not function as intended in terms of the smog equipment. Baring the fact that emissions tests aren't an issue, you will need to either install MILs on the rear O2 sensors or have them disabled in your tune so you aren't throwing an error light all time time. It also makes the car harder to sell later unless you keep all the original parts.