Most cat-back exhausts are SIDO, but only a few of them have a 45 degree exit. So you're probably going to have to get it built by a shop. What you can do to save money is buy the muffler and tips of your liking, then shop around at several shops to find the best deal, but be sure that they at least use smooth bent pipes. No self respecting exhaust enthusiast has crimp bent pipes.
08FX4 has several videos of his exhaust, which includes hi-flow cats, a single Magnapack, a Y-pipe to to make the dual exits, and 4" x 18" tips that are 45'd. That sounds like it would be suitable for you. I suggest you just do the muffler swap and add the tips, but leave the cats alone for a while. It might be perfect for you with the stock cats.