What to buy for replacing a Catalytic Converter

[completetech]

So I am throwing a 420 code and after having the mechanic look it over and diagnose it he said to get a new cat. So I am looking at replacing it and looking for some suggestions.

I'm rollin a
200 Chevrolet Astro RWD


Currently I would like to get http://www.andysautosport.com/chevrolet ... 32375.html as it is a high flow supposedly and with a discount it would be $395 shipped to me. But what else would I need or should I order with it.

My other option is http://www.partsgeek.com/catalog/2000/c ... erter.html and the Bosal 2938-05118780 for $299 shipped. But again does this have everything I will need? Should I also purchase a new muffler also, and if so. Which one would be good for overall sound / performance for a work vehicle.

Thanks,
Nathan

[WoodButcher]

Second link, it's cheaper, no need to spend more for a cat. Just be sure you wont toast the cat again, a poor running engine will cook them quick.
I used a walker sound FX muffler, sounds good no drone.

[completetech]

So should iI get a new muffler too or just hold off.

The van seems to be running fine so far (knock on wood). But thinking if I can get away not buying one then all the better.

[WoodButcher]

I wouldn't if it is not needed and your happy with the van as is.
I don't believe you'll get a great improvement in power or mileage buy buying the magnaflow but the steel may be of higher quality and thickness meaning longevity.
I bought a Y-pipe cat from Napa for my '97 back in '05 and just the last couple years I get the po420 code on the highway every so often but I clear it with my ultra-gauge and it won't come back until I drive with the same pedal again. I think I have an issue with the spider as she seems to run too rich.
I've gone through emissions testing here in CT twice successfully since this started happening.