Depends on the game. I have a Phenom II X6 1100T and I'm running Crossfired R9 280's which (together) are more powerful than either of those cards. My CPU's single core performance is probably about the same as yours. This setup crushes many games. However some games that are not well optimized cannot have those issue overcome by the raw power of the processor. Star Citizen is a good example, I get bottlenecking in that game.
Personally I would buy the card and just be aware of this issue. If the games you play have a lot of problems then consider an upgrade. The Phenom II chips were excellent and still hold their own against many current Processors.