I've got a Radeon HD6870 (Powercolor) and It's only been running for about two weeks, I haven't noticed anything wrong with it at all, but it does get a bit hot for my liking, GPU-Z reports:
Temp 1: 68.5C
Temp 2: 79.5C
Temp 3: 77.0C
Voltage: 1.17V
Is this normal? No overclocking, I just want to know if anything will happen due to these temperatures, as I am an avid gamer on this PC.
GPU Core lock is at 900MHz and the Memory clock is at 1050mhz, getting 250-270MH/s
Underclock your memory, as much as you can. If wont hurt performance (on the contrary actually) and it will lower temps a little bit. Even so those temps are uncomfortably high IMO. Try to improve air flow in your case or speed up your fan. If your card supports it, you can also try reducing voltage.