I had the same issue with an Integra I bought a few years ago, the cat was indeed clogged. If the engine burns oil, or the A/F mixture is off, added to the fact that it is a cheap aftermarket cat, it will clog up VERY quickly. The easiest way to find out is to just remove the cat and exhaust and test drive the car. It will be very loud, but you are just looking to see if the condition stops. If the car feels a lot stronger (which I'd bet money it will) then you need to replace the cat, and correct the problem that is fouling it in the first place. Like I said, I would look to burning oil because of worn rings or valve stem seals, or both. Try it, it costs nothing but an hour or so. Good luck.

Edit: the smell is also most likely a rotten egg or sulfur smell, which is attributed to the catalyst overheating. If it is severely clogged, you will be able to drive the car and then immediately look at the cat under the car, they can get so hot when clogged they actually glow red!