sp3arman

I have an '03 Outback that needs a new caty and O2 sensors. I have had a detailed diagnostic run by two different places and this is the consensus. I'm being told both by Subaru and by my independent mechanic that I have to buy the new caty from Subaru because the computer in my car won't read a caty not made by Subaru. This sounds insane to me and I'm trying to figure out how NOT to spend $1500 to replace all this. Does anyone know of a less expensive caty and/or sensors that would work? And, am I right to think that parts not made by Subaru will work just fine? Thanks