All AMD CPUs are backwards compatible down to AM2. ie, AM3 cpus are compatible with all AM2 and AM2+ boards. Theoretically.
This could require a bios update though to get the latest CPUs. Since you are using an OEM machine that's not possible. So really, you could only find the information about supported CPUs from Acer. Their information could be old though, so it's possible your computer could support the latest CPUs anyway. Sorry I can't be of more use.