Let's talk Cats (Catalytic, not feline)

[X5SND]

So with an intermittent CEL relating to O2 sensors (which are all working) and a distinct metal on metal slapping sound, I've come to the conclusion that one (or both) of the internals inside the cats have come loose and/or broken. Giving the cat a tap also confirms my diagnosis on one of the two....

Now for any of you who have had to replace them, you know they don't come cheap!! In fact it's a bit like bend over the counter....lol. Now my game plan is to yank the manifolds, cut out the cats and tig in some replacement high flow spun units....a quick search revealed that at least one other member had gone to aftermarket units, but it was either a 4.4 or 4.6.

If anyone has any input on the matter id appreciate it.....if I'm blazing my own trail here, I'll be sure to do a write up for anyone who finds themselves in this situation down the road!