Wouldn't be suprised if they did. Your temps are fine for overclocking. I overclock my whole silenced system...this means my fans are running lower, more padding, etc. Everything has been cake for quite a while now. Just watch the temps in the summer....
No really, with your xfx 5900 you should be decent up to about 450 gpu/850 or 950 memory range.
Let me know how you overclock that, as I am buying one soon.
Ben