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Keep us posted on how things go for you, I did the same upgrade a few years ago (without the firmware) and it has been awesome!

Got OS X 10.9 running on it (there's a thread around here on how to) and it just screams. Full disclosure though, I don't do any video editing, 3D rendering or anything like that. Biggest crunch I do is trans-coding MKV to MP4.
 
I just booted into Mavericks for the first time since I installed my new flashed ATI5850 graphic card. Wow, what a difference!

Everything is a lot smoother and Safari is especially responsive compared to when I was running it with the old 7300GT.

Not to mention I can use both monitors now....

MacDann
 
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