If you are planning to build a gaming PC, you should allocate at least 60% of your budget to your graphics card. A GPU is the most expensive part in a gaming PC and is very hard to upgrade it soon. Even if you think of crossfire/SLI in near future you must have a powerful primary GPU to make it work efficiently.
You can upgrade every other component in your PC slowly but not your graphics card. So buy a best in your price-point at this moment.