Try removing nvinject and see if you boot in low res, I think 10.5.4 could be too old for your 9800, I'm not sure but its worth a try. You may need a more recent OS X release or an updated set of Nvidia kexts to get graphics acceleration.
About the kexts, I would suggest using SMBIOSEnabler or SMBIOSEFI instead of a modded AppleSMBIOS. Also AppleATIATA should not be needed in AHCI mode and you dont have IDE drives (I'm not sure but I think some version cause kernel panics when using 4Gb+ RAM).