Good/Best nVidia OC software

I apologize if this has been posted before, I'm at work atm so I keep going back and forth between work and webpages.

I was wonder what a good (or best) nVidia OC software is? I have a little experince OCing ATI's as my last rig had a X800Pro which I used the ATITool with suprising results. I say surprising because I was amazed how big of an improvment OCing made and how high I could run it OC on a stock cooler.

I honestly thought with stock coolers that GPUs and vid Ram was stock at it's near highest heat limit possible for a stock coolers but I guess I was wrong.

I'm looking to OC two XFX 7800GT's and was curious about how high you guys think I could get them for now on stock cooling and what is considered "too high" of a temp for them to run at? And what program would be good for trying to do this. Eventually I'll get an aftermarket cooler like Zalman (though I don't think two will fit with my PCI cards), or nVidia Silencers or something but not for a while.

The best is riva tuner no doubt about it !

coolbits is good but has much less feature and tweak capabality.

Check it ou there : http://www.guru3d.com/rivatuner/