Make Photoshop faster on a budget?

A reader sent me a question:

I’m a semi-retired freelancing graphic designer, currently using a desktop HP Pavilion P6-2114 with an Intel processor (i3-2120), Intel HD Graphics 2000 with an Nvidia graphics card (GeForce GT520). I work in Photoshop 3D and it’s really slow, with only 8G of RAM. Any suggestions to make that app run smoother and faster? Can an AMD product be put in this tower? WHICH ONE? Most bang for a small buck on a budget? or would just more RAM help? Thanks!