I use ATIinject too, it gives me the right resolutions but not CI/QE.
When I tried the kexts from 10.5.1 I get CI/QE but with those stange black menus..
If you have a working x1650 in 10.5.x, please tell me what install DVD you used, if you applied the graphics update 1.0, and what files you altered.
I tried to use the IONDRVSupport from 10.5.1 too, but then all I get is a blue screen with cursor..