Chart below shows dependence on processor score in bottleneck calculation with AMD Radeon HD 6900M graphic card for General Tasks.
We don't recommend you to downgrade your processor if you physically own it because there is no good reason to replace current processor with weaker one. Here is list of processors that will best work with your AMD Radeon HD 6900M graphic card. This processors with AMD Radeon HD 6900M will have less bottleneck than with your current AMD A4-6320 processor.