Stock '01 4.2Q exhaust.

Any suggestions as to best price/performance benefit of:

1. Replacing only the damaged cat with aftermarket/OEM parts.
2. Replacing the entire exhaust with aftermarket/OEM cats and catback setup.

Eeeebayyyyy has some cats for sale on line, but dunno if I could trust them.
I'd like to see if maybe anyone has a lead on a complete aftermarket setup (Milltek, Magnaflow, etc...)

Thanks in advance.

p.s. I've read a lot of threads regarding what people have done, but that was done mostly on purpose, not because of a fault.