A few months ago AMD created quite the confusion when they released the HD6870 and HD6850, two GPU's that contrary to their naming did NOT replace the HD5870 and HD5850. The reason for the naming change was that AMD wanted to rearrange their naming scheme and use HD69x0 for the enthusiast/high-end GPU's like HD6990, HD6970 and HD6950 while leaving HD68x0 for the performance cards.
Today AMD finally has released two of the HD69x0 cards: the HD6970 and the HD6950, both replacement for the HD5870 and HD5850 respectively. The following image illustrates how AMD sees these two GPU's:
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips