5870 Overheat

It has been almost about a year since I last purchased my new xfx 5870 video card from Newegg last september. The first few months, I had no problems with the video card. Now that I try to play any game, the card overheats up to about 70C and the fan speed increases up to about 65%. I tried running various games with all low settings and all high settings, but the card still get as hot and the fan speed still increases up to about 65%. I have not overclocked or manually set the fan speed of my video card.

Here are the specs of my computer (none of them are overclocked):
AMD Phenom II 965 Black Edition
Asus M4A89TD PRO
Corsair 650W TX
2x2GB G.Skill Ripjaws 1600
XFX 5870
Windows 7 64bits

I have already contacted customer support from the xfx site. This is what I said:

It`s been almost a year since I bought this video card from Newegg. The first few months when I started using it, everything was fine. I was able to play most games on high settings without any problem. A few months later, problems started coming up with the video card. Now every time I try to play a game in full screen, even with the lowest graphic settings, the temperature of my video card rises up to about 70 degrees Celsius and the fan would start to get really loud no matter what game it is. I was wondering if I could get any help or advice on solving this issue. I also haven`t overclocked my video card or anything.

This was their reply:

Hello Ying, thanks for the message. 70C is actually really low for these cards. We expect them under full load to reach the high 80`s or low 90`s C. The fan is supposed to speed up as the temperature rises I believe around 70C its only running around 35%. What your describing sounds normal. William.

I personally don't think that this is normal because every time I try to play a game, the fan speed of my video card gradually increases up to about 65% tops. Also sometimes, the games stutter or lag while I move around. If I could receive some advice on how to solve this issue it would be greatly appreciated. For the record, I have not used up the warranty yet, so maybe I could send them my video card and get a new one, but that would my last option if nothing turns out right.