Here is your ASRock CPU Support list: https://www.asrock.com/mb/AMD/A320M-HD/index.asp#CPU
See which one is within your budget and BEFORE you install any new processor make sure YOU UPDATE YOUR BIOS to the latest version to prevent your new processor from not being recognized.
When you update your Mobo BIOS make sure your READ ALL THE RED AND YELLOW NOTES before updating.
EDIT: Please correct your Thread's Title you have written that you want to upgrade your GPU but in your thread you mention that you want to upgrade your CPU and not your GPU.
