I'm wanting to do a custom 2.5" exhaust from the cats back. I would have separate pipes from the cats going into an x-pipe. From there, it will be straight all the way back.

Does anyone have a sound clip with something similar to This?

 

check out some sound clips of the fast intentions system. It has a 'merged' X pipe design where the two pipes are welded in the middle to form a 'X'. Sounds very good IMO. Also, check out some videos of the magnaflow resonated X. Seems to be a staple component in all custom set-ups.