Something to think about.
Almost any head you buy will require a core, you must return a head of like kind. At this late stage in the game, it's been 8 years since the last model year that used a SOHC - 2004, most any reworked head you get will be one that has previously dropped a valve seat in the past.
And as you have seen they suffer damage, sometimes to a great extent. The head you have on your car that you are thinking of replacing to avoid the issue - hasn't dropped a valve seat, yet? And you know the mileage on that head.
Sure they test the heads for leaks but you will have a head with unknown mileage and parts with unknown mileage. Plus thread holes may need to be reworked - helicoils.
So if you know your heads mileage and condition. Give some thought to having IT rebuilt per AERA standards.
But, It looks like there is an after market head available, NEW with updated seats, that is being cast to replace the SOHC SPI head. I think I saw it on E-bay.
Member of the Dropped Valve Seat Club.
Replaced #4 Piston, Rings, Rod+Bearings, AERA Re-Manufactured Cylinder Head and a light Hone. Then CLEANED the hell out of everything.