I was going to recommend GraphicsEnabler=n but when I tested it on my system with a GTX260 it gave me a black screen(monitor in sleep mode). Go figure. I'll be posting a new ISO later, there doesn't need to be need to be a separate 32 bit one. So you would just use:
As far as your clock speeds, have you run Geekbench(google it) to verify the numbers? It might actually be running faster but just showing the wrong numbers. You can modify the SMBusspeed value in /Extra/smbios.plist to adjust what is shown in System Profiler but it's not necessary. Also, make sure you installed the Processor Independent DSDT from the installer pkg. You should select one and only one option from the 3 DSDTs, either 920, 940 or Processor Independent(in your case since you have a 965)
I will try the geekbench and check it
Actually, the beta worked fine without arch=i386 but not when i added it. (gave me a bunch of sound errors). The thing i needed was the GraphicsEnabler=no.
I used the processor independant DSDT so that seem to be ok (it reports my i7 960 correctly too in "About this mac")
As a side note, sleep works just fine here too and the graphics worked fine after i woke it up too. And it reports both my GPU's in "more info"
Next task is to tacle my Acer Aspire 6920g .. i suspect that will be a much tougher fight...