Spend the extra $10 bucks and just get the FX-6300. So you can upgrade from the 6 to 8 core variants.
However, how many times will you upgrade your CPU in say, the next five years? If you build your PC properly and balanced, the CPU and/or motherboard should be the last component upgraded.
But the most important question is, do you currently have a motherboard? If so, upgrade to whichever CPU is supported by that mobo. If not, then get the FX-6300. The FM2+ sockets are for APUs. They are still good processors in of themselves (the A10 series at least), but you would be paying extra for a feature (integrated graphics) that you will not use. The AM3+ will allow you to upgrade to the 8000 series. But honestly, with the 6300 OC'd, you...