I can't comment on the Xray, but I don't think you can go wrong with either a YZ-2 or a B6.
I personally run a YZ-2 DTM that's had a few bits fitted to bring it more or less inline with a CA (steering plates, gear diff). A good used CA would be just as effective, the differences are quite subtle. In terms of steering, it's got an extremely positive front end.
Spares are easy to get hold of for both cars, and there's loads of setups available. As usual, used prices are tanking because of the version 2 kits - which are really just minor upgrades. I picked up a YZ-2 CA purely for spares a few months ago for £100
