ATI Radeon Control Panel?

well, i am using a G4 DP 1 Ghz with ATI radeon 9000 pro graphics card, and it has a control panel.
just check ATI's web site to see if there is one for intel mac's

I have a 17" iMac and I couldn't find anything on the ATI web page.

ok. here is the idea. your imac has a built-in LCD display, and it has all necessary configuration had made for it. For color calibrating use Displays preferences panel.
As LCD displays can use all the monitor area and it is flat you do not need to configure the position or the height, width, pinchusion or rotation.
Also software updates for your graphic card comes with-in system update packages.

but one last point should not be omitted. apple produces different lines that are suitable for home, office users or professionals. iMac's are, i guess, always thought for home&office users, not for professionals.
For example, my iMac 400DV is not suitable for upgrading or smtg else, but my 1Ghz DP G4 is completely designed for it. i have also ATI Display control panel installed on my G4. Apple certainly classifies users. and i think this idea really works.

it's an interesting question because if you run bootcamp on the iMAC, there is a control panel in windows. I'm also able to run a 1920x1080 resolution from windows while I'm not from MacOS on the same iMAC (20" Intel). While apple has constrained the use, it seems a bit too constrained and having a control panel for MacOS would be great.

There is a utility for the X1600 that you have that does what you are looking for.

It will check clock speed (that's how I found out the card in the iMac is running at full 400 Mhz instead of the reduced speed on the Mac Book Pros) and it will allow you to overclock the GPU and Video memory if you dare.

However, at this time the utility is only available for Windows so you can only use it when you are running Boot Camp. And, all settings revert to the original speeds when you quit that session either in Windows or when you log back in to OSX.

Hopefully one of these days we will have a similar utility that runs under OSX but I would not want to overclock the card anyway and the Windows utility at least let me know the speed the card is running.

If you would like to try it and are running Boot Camp, it is available here:

http://www.techpowerup.com/downloads/259

Not really the answer you were looking for but the best we have available at this time.