The Catalytic converters should have a warrenty of 8year/80K miles.
Were you covered?
I would of had a back pressure test on your cats at a local muffler shop for a 2nd opinion.
If bad
http://www.catalyticconverterwarehouse.com is the place to buy OEM cats.
$300 for a direct fit, consider an aftermarket cat instead.
I wouldn't trust any service shops, the throttle body could of be cleaned.
You should of came to AF 1st.