You need to start at the beginning... There's a LOT of hardware on your MB - just a quick look at newegg.com reveals:
- nForce 590 SLI MCP chipset (check to see what support it has - SLi chipsets can also be problematic)
- 2 LAN adapters (the infamous "nforce networking adapter" and a gigabit Marvell)
- NV RAID and an Sil 3132 ??
- ADi1988b audio - you may find support for this one but it can wait until you're out of safe mode
- doesn't say what WIFI chipset is used

Personally, I would disable and/or remove everything but absolutely essential hardware, boot using -f, and see if you get into the OSx86 Desktop. If you do, start adding hardware back in until something breaks it again. Your LAN adapters may need special attention (I'd disable them right off the bat). Hope you're not using RAID. Audio won't stop the install. WIFI might. The main chipset may need the proper .kext to make it work as it should...

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Running both 10.5.8 and 10.6.4 on my stinking AMD/ATi machine...