CPU w/built in graphics & equal GPU

I'd like to pair a CPU with built in graphics with the corresponding GPU for an inexpensive gaming rig for my daughter in college. I'd like to run crossfire to get the best graphics for the money. I'm currently looking at the AMD A10-5800K CPU with integrated AMD Radeon HD 7660D graphics in the ASRock FM2A85X Extreme6 motherboard.

What GPU would be the equal to that to run crossfire?

The Radeon HD 6670. Any brand, and almost every single motherboard for sockets FM1 and FM2 support dual graphics. Also, excellent choice of APU for the task, this will likely be capable of running many games at 720p with medium to high settings. For most tasks though, it will probably revert to only relying on the dedicated graphics, as they are stronger than the integrated.

OK AMD has come out with the new A10-6800K with Radeon HD 8670D integrated graphics. Very cool. However, what GPU would equal the 8670?

The new 6800K's intergrated GPU is equal to current gen's 7750, if I'm not wrong, which makes it quite capable playing modern games.

Also, the namings of the intergrated and dedicated GPUs are different, so comparison would be from their performance, not their names.

OK so the fact that the APU has 844MHz worth of GPU and some 7750's have 850MHz would make them "equal", right?