Yes the Phenom X2 720 will bottleneck it, it's architecture is extremely outdated and wont be able to keep up with the card. If you have an extra $100 to spend, I recommend buying a A75 AM3+ motherboard and a Phenom II X4 965, that'll ease the bottleneck (I'm not sure if it'll still bottleneck it since the 965 is fairly old of age as well, but it's not a dual core at the least)