11-Way AMD Radeon GPU Comparison On Linux 3.12, Mesa 9.3
The Radeon HD 5450, HD 6450, and HD 6570 graphics cards can be fine for running a composited desktop on the open-source drivers and other light OpenGL acceleration, but certainly not for gaming.
Remember, these results are from using the Linux 3.12 kernel and Mesa 9.3, plus enabling Radeon Dynamic Power Management. If using a stable Linux distribution right now, the OpenGL frame-rates you will encounter will likely be less.