[4valve 4tw?]

In the end it comes down to grand total price, and if you got a deal on a cat back and are installing it in your driveway, it's usually worth it(especially for us North easterner's dealing with 15 year old, crusty, rusted metal).

If you know what you want, and aren't going to be spending more and more chasing a certain sound then the catback is one and done. If mufflers are $70 a piece let's say, that's $140. Maybe $80-100 for a shop to cut your old mufflers out and put new ones in. You're looking at $220-240. That's a decent discount vs most catbacks, but what's another $250 if you're keeping the car for years? Just wait for the catback you want to pop up used, and save yourself some money. You already have the midpipe, may as well match it up(plus, you get a good size set of exhaust tips). Not that the mufflers aren't the bulk of the gains, but it also helps each mod moving forward if you have plans.