Many people advocate buying singles, but I'm not one of them. I've found singles to be horribly expensive esp for a continuous print item. The kihraxz (as well as a few other ships) has plenty of cards favored in the current meta so you'll have good trade stock anyway.
I'd recommend upgrading one kihraxz to a yv666 however if you can spare the cash. There are a bunch of upgrades in that set that don't come with any imp set either eg engine upgrade, lone wolf, stay on target, etc. And if you one day decide to try play em, you'll find 5 is the max kihraxzs you can fit in 100 pts