It turns out one of my catalytic converters was bad.
I called up the dealership to find out how much it would cost to replace. They said that I needed to replace the whole Y assembly because the catalytic converters are built in. They asked me a question pertaining to the model of my car and since I didn't know the answer they couldn't quote me the exact price. They did tell me that the price range for the Y assembly on my vehicle was between $1,100 to $1,300 but that there was a certain muffler shop nearby that would cut out the bad piece and weld in a new one for a lot less.
I called up the aforementioned muffler shop. Turns out that for $160 my problem would be fixed. It was a no-brainer.
Now I have a different noise altogether that I've traced back to the new converter. It only happens whens the car is cold, another rattling sound of sorts.
After putting in the new converter I discovered (by reading other articles at this site) that I could get an aftermarket Y assembly for about $400. If I would have known that at the beginning, I probably would have. Now though, I beleive my car for all practical purposes is repaired. It's just got an altogether different noise sometimes but if there's nothing to fix, I may just have to live with it.