Based on a dealer diagnosis, I replaced the cats (all 4), 92,500 miles, '98 AWD to the tune of 1300 at my shop. At about 120,000 miles, was getting codes again and was told it was the cats again, and they were just out of warranty. Got smart, got a code reader. Showed P0420 and P0430 codes. Eventually got a P0153 code, which is Bank 2 O2 sensor 1. I replaced all 4 O2 sensors at 140,000 miles and have driven nearly 40,000miles without a code until just recently started getting P0430 again. I plan on spending about 60 bucks for Bank #2 sensors before replacing any cats!
My suggestion is to replace the O2 sensors. There is a wonderful post on how to replace 3 of them by removing the center console. 30 to 40 bucks apiece sure beats 1300 to get a car to pass inspection.