Ack, sonic snap does allow SR. I guess I'll have to use arcane thesis shenanigans for some cantrip level consecrated scorching rays instead. Not an issue, really - I'd have to spend 825000 gp to get all 1650 of them installed - in other words, 12500 gp of real money, plus a bit of overhead to make the castle teleporty.
Damage = 4d6, half is consecrated, half is subject to fire resistance 6. Average damage is 7, so have to hit with 82.5 rays.
Hit only on natural 20, so I'll need 1650 rays. Shenanigans render these cantrip level scorching rays, so I'm buying them as magic traps/spell turrets for 500 gp a pop. If I wanted, I could buy the whole stronghold as a single item with merchantile background for 25% off, and there's a whole bundle of stronghold discounts I can throw on, but... no need to go into detail.
Oh, and uncanny forethought mark of justice him. Just because.