I would think that the XFX cooler would be quite good already. You should be OK to overclock a little. It all depends on how much you want to overclock. Did it come with monitoring software? If the temps are below 70C you're laughing. They can handle more than that though if you really want to push it.
If you want better cooling, I would try to get good airflow in the case first, such as cleaning it, putting an extra intake on the bottom, better fans or even just turning them up in the BIOS.
If that is still not enough, you may need custom water cooling and a water block for your graphics card. This is the most expensive option and may not be the best option for you.
Thanks Jay-Z. I always knew you were a great(not) singer.
Anyways, I'm about 86 on furmark, that's okaay, right?