You chipped your core. You need to be much more careful when removing or installing your heatsink or it will happen to your 2000+. It has nothing to do with your overclocking attempts.

As for the Volcano 7+, yes it is better than the default AMD sink, but that is because the default AMD sinks are the cheapest and crappiest sinks available. The Volcano 7+ will hold up to SOME of your overclocking, but as soon as you get either a hot day, or try to push the overclock particularly far, you will run into thermal problems. Like I said, there are much better AIR-based solutions available.