Any luck finding Ammo?

With your arsenal I would fore go the Saiga. You already have the AR. Every home should have a shotgun. Semi autos are as low as $700(good ones). But a nice 12G Mossberg should do the trick. Semi auto 308 185 grain rifle like a SA M1A or SOCOM will finish off your arsenal real nice. Those are good to a 1000 yards equiped with the right scope and good eyesight!

Only reason for the Saiga is the wife wants one, otherwise, I wouldn't get it. She wanted the 5.45, but she'll get the 5.56 so I don't have to keep too many kinds of ammo. A Mossberg 500 or 509 is what I have in mind for the Shotgun; good quality and good price, plus I've done quite a bit of CQB training with them, so I'm familiar with it (and the sound of pumping a shotgun should be enough to deter most would-be thieves).