[Felix The Assassin]

I would say how much can your system handle? Is your system capable of handling a superior graphics card? Can your PSU handle the extra load plus extra heat generated by the product? Ever thought of why most of those other brands have BIG LOUD fans on them? Ever thought of water cooling?

Big bad video cards do not come in stock machines, they would literally melt it down. That includes the other brand as well. Ever looked at a custom rig and wondered why in the sandhells is there so many fans?
Did you by chance overclock your system? What about the vid-card itself? There are numerous overclocking programs that will kill a card and or system.
ATI cards are very hard, very fast, and need lots of cooling as well, but they choose to put a single fan on their boards, with the understanding that most systems that run a higher card are not stock.
I run ATI, and despis that other brand. However, I also have massive cooling, and a superior PSU to go along with OC'd CPU, Memory, and ATI 9600XT. I can run 3 hrs heavy (ALL Options Maxxed) 3D programs, and have a CPU temp of 129*F with a case temp of 89*F, and vid-card temp of 150*F without any pixelation.

In order to achieve a superior performance, you must start with the basics for said layout.
how many uncluttered intake fans do you have?
what size are they?
how many exhaust fans do you have?
what size are they?

I'm sorry if you had a bad experience, but a little bit of extra cooling will go along way. In addition, if you go with that other brand, your stock PSU will be working overtime to keep up with the power demand, again you will be faced with a heat issue.