I have an old HP Pavilion p7-1254, and have recently fitted it with another new graphics card. I originally put in a GT 720, and it was okay, but a few days ago I put in a GTX 750 Ti, which runs quite well (at least for my standards), but in a lot of games now, the stock AMD A6-3620 processor is bottlenecking the system, especially in more CPU-bound games I would like to have better performance in, such as Minecraft and Project Zomboid, where the GPU in those games at moderately high settings only reaches a max of around 15-30% and 5-15% respectively. I will most likely be upgrading the PSU soon to a 500W power supply from the 300W that comes with it. I don't know much about getting all of the CPU compatibility stuff right, and my budget is quite strict, so I'd prefer not to buy a CPU and then it be unusable
. Thanks for any help! 
(Also sorry if this is in the wrong category, first post)

(Also sorry if this is in the wrong category, first post)