Tried that, with no luck (GraphicsEnabler=Yes is in chameleon.boot). Installed Lion with the Unibeast method and everything worked (mostly) OOB when I booted with the Intel 3000. With the XFX 5670, on the other hand, I wasn't able to pass the Apple screen (the wheel stopped turning and the system froze). Weird thing is that the card is recognized like this:
ATI Radeon HD 5600 Series:
Chipset Model: ATI Radeon HD 5600 Series
Type: GPU
Bus: PCIe
PCIe Lane Width: x16
Vendor: ATI (0x1002)
Device ID: 0x68d8
Revision ID: 0x0000
But if I change the DVI connector from the onboard Intel to the XFX DVI, the system doesn't boot, too.
Any tips? (and tks Toleda for the answer)
Little post edit: when I change the connectors I also go into the bios and set the XFX as my primary video card.