According to Intel, the g43 express chipset is bios compatible with the Q9650, however that's just the chipset itself, that's not ECS or Acer compliant, who use custom bios to include or deny certain cpus, usually based on higher grade models. HP, Dell, Sony, Lenovo all do it. They want you to spend more for the upgraded cpu model, not buy the cheap model and swap in the better cpu.
You could try the Q9650, but it's a 50/50 shot of working, the mobo either accepts the g43 chipset bios or it accepts the ECS bios for the G43T-AM3.