Nissan Repair: 2000 Nissan Maxima GLE Cat Issue, nissan maxima gle, muffler shops

Question
I have a 2000 Nissan Maxima with 138k on it and it recently failed inspection with the code P0420.  I then took it to the dealership and they said the left and right cats need to be replaced and quoted me about 1600 to do the job.  I have since been trying to price them aftermarket myself and I am getting conflicting information about the # of cats on my vehicle...some places list 2 and some 3 and none of them are listed as left and right.  While at the dealer, they installed some software updates and the CEL went off and has been off ever since.  Therefore, here are my questions:

1.  How many cats are there?
2.  Will they need to be replaced anyway now that the software updates have made it go off?
3.  Knowing the price difference between after market and OEM, which should I go with?

Answer
Wayne,

You have one big one under the car and two up front.  It is called a three way system.  If the converters are indeed bad something had to cause it.  I would go with aftermarket if they do need to be replaced since the factory ones are way expensive.  They do the same job and it is not like they are chrome or anyone can see them.  They are under the car.  I would check around at local muffler shops and ask friends which shop they have had luck with before I would go to the dealer.  Quality and price are both considerations.  But, the aftermarket ones are fine.