4" Cat back exhaust - Worth the expense ?

[eop002]

Wondering what benefits I can expect to see in going to a Mufflex 4" cat back w/Borla XR-1 from my existing ATR 3" w/Pitbull muffler on my TTA. Exhaust is on a 274ci StageII , GN1R, PT70 HPQ turbo with a 3.5" downpipe all the way to the gutted cat.

I wanted to get general consensus if spending money in the 4" exhaust is worth it as compared to using for someother upgrade.

Thanks
Oscar