740 is DOA- is an aftermarket catalytic converter ok instead of oem?

["Stephen Robinson" <stever@xxxxxxxxx>]

I am having a huge problem with my 95 740i - been in the shop for a week as
it lost all power on the road last week after hearing a loud banging sound
(?) under the car for the past month (only when it warmed up for 40 minutes
or so...).  They tell me at Excluservice in Rockville, Md. that the
catalytic converter is completely clogged and no air is getting through,
thus, no power - and I need a new one just to figure out what the real
problem is!  They said an oem one is about $1165 and an aftermarket one is
about $565 so I told them to go with the aftermarket one.  Did I chose
right?  They have to order it.  They said it only had a 2 year warranty on
it on the aftermarket one, as opposed to the BMW one which is longer, I
suspect.  Anyone have any experience with this? 
Hoping this doesn't turn out to be a majorly more expensive repair,
Steve Robinson
1995 740i  not running!
1988 911 Carrera - always runs like a top

------------------------------