I cannot help you with your request for a recommendation, since I've not used AMD processors anytime in the 21st century.
I just want to take up the claim of "decreased performance". In general, a processor won't decrease performance over its life. It will always operate at the same frequency and with the same performance characteristics.
Of course, this assumes that it does not get throttled from external factors, such as increased heat due to dust build-up or a failing power supply (that can decrease it's performance over time, since the capacitors, etc. may become degraded).
What does happen is that the applications and games become more demanding, and also that the installed application base over time will build up and add many programs and tasks that are active and resident and will drain the resources of the processor.
Sometimes a remarkable improvement in performance can be achieved on an old processor or computer by simply re-installing the operating system and then taking care what applications are installed.