I'm thinking of replacing my old AMD Athlon 3800+. I read the "Best Gaming CPUs For The Money: February '10" article and thought Athlon II X3 435 would be quite reasonable, but as it turned out my mb doesn't support it for some reason. So I'm here to ask which CPU to get for M3A78-VM considering price and performance. Preferably under or ~$100.
Your Motherboard is quite capable of the 435 yet it seems as if ASUS had not updated their CPU support list. Chances are it IS supported, but not listed. This actually happened with my Asus M3A, a lesser cousin of your motherboard which "officially" does not support Phenom/Athlon II CPUs, but correctly recognizes them with the latest BIOS (I have a 435 running incredibly on it).
But, if you do not wish to take any chances, the Athlon II X4 630 is 100mhz slower but has an extra core, so you can't go wrong with it.