I forgot to mention, I pulled the 5870 and replaced with a 6970. The 5870 ran at 90C+ the 6970 which should run warmer sits at a happy 74C at 85% fan. The 5870 was at 92C with 100% fan. Both units use the same single-fan Powercolor heat sink.
The 6000s run cooler than the 5000s because they are normally more efficient with the power draw. I say "normally" because, cheap cooling, vrms and phases can and will make a stock 7870 run hotter than an overclocked 5850. lol