I guess there's only one way to find out... All I get is conflicting information about the QX9300 working in a iMac8,1, that's one of the big interrogations I have about this machine, next month hopefully, I'll be able to prove if it's possible or not. If it proves not to work, I think I got a laptop somewhere that takes socket P chips and could use a QX9300... Not a big deal.
GPU-wise I think it has a Radeon 2600XT, I would like to replace it down the line with either a 8800GS or a GT130 from a 2009 iMac, assuming it's possible in the first place? Slot-wise I'm sure it'd be a 1:1 fit, but what I'm worried is that Apple may probably have put some software locks in place to prevent that... Knowing myself, once I get that "curiosity itch" it's hard for me to resist the urge to test things out and find out.
EDIT: Regardless, here's the thread that I saw and briefly mentioned the QX9300:
https://forums.macrumors.com/threads/can-you-upgrade-the-cpu-in-an-aluminum-imac-early-2008.885917/
...I guess I'll try and document my efforts on a thread to fill in the blanks... But at the same time, given how expensive QX9300s are (I found a seller in Germany asking ~119€ shipping included for one of these), I'm having second thoughts, but at the same time, as I stated previously, I may have a laptop that supports QX9300s so it wouldn't be bought in vain.