Haoshiro Eidorian is right, the HD 2600 Pro is not a mobile GPU. You have been misleading people with your thread.
It's true the iMac was never a hardcore gaming machine but i think a lot of people were hyped up because of WWDC and the appearance of EA and John Carmack and thought that soemthing special was going to happen.
Even though iMac aern't really for gaming it certainly doesn't deserve a sub $100 GPU. You are paying top dollar and getting a sub $100 card? Does it make sense to you?
I've seen the frame rates of the HD2600 Pro they are horrible. What's the point of having a DX10 card, if you can't run any of them with the eye candy?
Yes, they have Mobile versions of the HD 2600 Pro.
The last generation iMacs used Mobility X1600 cards, why would anyone assume that isn't the case with these new macs? I have the older machine, and I have Boot Camp installed on it, it's definitely a Mobility X1600.
Now if you have some proof that isn't the case then by all means share it.
My new iMac with an HD 2600 Pro will be arriving tomorrow, I'll be doing comparison benchmarks and analysis of them both at that time.