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This guy sells lots of converted cards.

Checking this eBayer's feedback he has sold many converted cards to happy customers, he could be worth trusting just to find out if this thing does work, his return policy is clearly stated.
He claims to work with Rominator, I'm off to Netkas.org to check that out....
 
Even if you can flash it to work on OS X you likely won't be able to use both DVI ports, are you planning on using this with two monitors? Why this card? For the same money you could get a AMD 5770 which is a fantastic card and supports three monitors.
 
Even if it works now, the future is unclear. In the past, OS updates have broken compatibility with flashed cards that were once considered rock solid compatible.

I think getting a flashed card is fine as long as you know what you are getting into and accept the fact that it may turn into its own hobby.
 
Exactly, you might as well build a Hackintosh then as the possible unstable elements introduced by updates can make it a real pain. I came from a Hackintosh and simply got tired of wondering if my main computer would work after an update or what might be affected and then also about the future of Lion. I picked up a used Mac Pro and then upgraded the video card with a used Apple 5770 on Ebay, works fantastic now and I don't have to worry about updates, ever.
 
I was just wondering if these worked because I haven't read much about people having success flashing them. However, I have a 4870 1gb in my pro right now and I wouldn't mind a tid bit more horsepower. I just recently purchased 16gb ram for around $300 so I think the GPU is my next best bet.
 
I would go for a 5870 instead as they are more typically supported in Mac OS X and less likely to be crocked by an update. The GTX470 is about the same in performance terms unless you want heavy CUDA usage.
 
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