I'm running the appended setup, and I'm looking for an extra little boost in gaming. I know I'm a long way off the state-of-the-art setup, but I don't want to spend much because I'm looking for a major upgrade once Bulldozer, AM3r2 and PCIe3 come along.
The performance gained by Hybrid CF really isn't worth sticking with the older technology needed to make it work. Adding a $20 HD3450 or HD3470 will be okay for general computing, and even light gaming, but don't expect much regarding Hybrid CF.
If you went with a HD4550 or HD4650, you would be better off than with the Hybrid CF solution.
My recommendation, the more oomph would come from the HD4550/HD4650 (especially a DDR3 HD4650). However, hard to not want to play with a $20 Hybrid CF solution as long as you don't expect the moon in return.