Stock Cat Busted - What to replace with?

Sorry to invade the 4.6L forums again, but no one posts in the 3.6L forums anymore, and when they do, they don't generally know too much it seems.

I don't know how I did it, but I busted my drivers side cat. I noticed a rattling noise, and yesterday I knocked on the cat and it rattled like a can full of rocks and the heat shield seems pretty solidly in place, so it seems like the guts cracked (the passenger side cat is still fine).

The OEM cats are pretty pricey, if I did my research correctly, moreso than aftermarket cats.

I know that its not going to have much performance effect, but from a cost standpoint, whats the difference between getting the stock cat replaced and putting in a set of aftermarket cats?

I do a lot of my own work on my car, but I've never done an exhaust and I don't weld so Id have to have someone do the work for me no matter what parts I decide to use. I also havn't spent any time looking into aftermarket parts because, after all, its a V6, and I decided a long time ago that it wasn't worth the effort to mod it and eventually I'll just get a GT when this car is ready to die, so I don't know much about what my options are here.

Any help would be greatly appreciated, thanks.

I meant 3.8L, just a typo. Its hard to forget since most toilets are 3.8L per flush (Kind of comical).

And by an aftermarket exhaust, I meant more getting them both replaced. Looking online, a brand-new MAC H-pipe with two cats is $369, and I saw one site that priced an OEM Ford cat at $460. Almost $100 cheaper for TWO cats plus the pipes? Seems kinda ridiculous to me. But like I said, I'm not an expert on these sort of things which is why I asked. I wouldn't do two different cats though, that just seems like a bad idea.

And yeah, NJ has emissions so I can't gut them or replace them with straight pipes. I've also heard some aftermarket cats have trouble with passing emissions, which is another concern, even if "rated" for 49/50 states.

I'm going to talk to my mechanic and see what he has to say as well, but when I have to use him I like to go in knowing what I'm talking about. I trust him, but I still don't like going in blind.

Junk yard may not be a bad idea, though.