Look at some benchmarks and see how the processors compare. For example in Adobe Photoshop or in Blender the Intel Core i5-3570K and the AMD FX-8300 did pretty much the same. The Intel won by 2%, not a noticeable difference in real life IMO.
http://www.tomshardware.com/charts/cpu-charts-2012/-33-Adobe-Photoshop-CS-6,3169.html
http://www.tomshardware.com/charts/cpu-charts-2012/-03-Blender,3162.html
When buying a PC for work, don't skimp on the CPU. It's the most important part. For example with the FX-6300 you save $100 compared to those other two, but it would take 20% more time for the same thing. Who would you rather be, the guy who spends $900 on the PC and works Monday to Friday, or the guy who spends $800, has a cheaper CPU, and works Monday to Saturday (that is, 20% more time) to achieve the same thing?