Your CPU is probably going to bottle neck your system. If you can't afford much an AMD CPU is a better option. I got a Phenom II X4 at 3.3GHz, and with a ATi Radeon HD 5670 it runs TF2 at 40-50 fps at 1600x900 resolution. If I increase my resolution to 1920x1080 (1080p) it plays at 25-30 fps. Also make sure the AMD CPU has a AMD MoBo that it works with, Intel and AMD CPU's need different MoBo.