I dont' really see how you're considering the world sport which is a chambered muffler and then your other choices are the T1R or an SMSP 2.5" exhaust...

If you're planning on going with a header with a 2.5" collector, it would probably be a wise choice to get a 2.5" exhaust now. If you can't afford everything at once, I'm actually selling a used carsound cat with flanges welded by hytech which would facilitate this. It's has a 2" inlet for USDM headers flared to 2.5" at the outlet.

Another choice for a custom exhaust is hytech.