Honestly, you're at a really good spot still. I would say if anything, I would go PSU, 120hz or large format monitor, and eventually a new videocard. 7xx or 8xxx will probably be your best bet. Put some funds in a savings account for Haswell, which is the next CPU architecture change. You could OC your CPU a bit more too if you wanted.
Remember when you start to hate one side, the grass is always greener on the other side. You are complaining about AMD issues, but look at even the past 4 posts. All NVIDIA driver issues.
You're not really going to see any significant gains from upgrading a 6870 right now. If you have specific needs, like 1440p resolution or 120fps/hz, then I might suggest something else. But if you're in the 'plays great at 1080p' category of desires, you're still set.