Well Asus has already released a bios for my P965 board(P5B-e) that supports QX9650 so I assume it will also support lower end yorkies as well.
The only problem is with the low multi's 7.5 on the 9300 and 8 on the 9450, I could never reach the overclock potential of these chips (over 4ghz) with this board as it will require well over 500mhz FSB and this board hits its limit right around 500mhz. If the price for the 9450 ever becomes reasonable I may get one, as 8x500 4ghz would probably be doable.