Upgrading Video Card in Early 08 Mac Pro

I have an early 08 Mac Pro with an Nvidia 8800 GT and 10 gigs of ram. I want to upgrade for video editing as well as gaming. I game in PC as well. Is it true I have to buy official Mac video cards? That would be easier right, rather then dealing with flashing the cards and etc? Would the Ati 5770 be good enough or should I splurge for the 5870? Is the 5870 that much better that it's worth the extra 200 dollars? What do you guys think, since my comp is kinda old would the 5770 be a big enough jump?

Also, is it easy to install these cards? Do I need tools? For bootcamp, how do I install the drivers for windows 7? Do I download and install the Ati drivers before I put the card in?

This is the 5770 I am looking at...
MC742ZM/A Apple ATI Radeon HD 5770 Graphics Upgrade Kit for Mac Pro, Mid 2010

Here is the 5870 I am looking at
MC743ZM/A Apple ATI Radeon HD 5870 Graphics Upgrade Kit for Mac Pro, Mid 2010 or Early 2009

Thanks in advance!

Matter for you if you want a flashed or a Mac version card. The 5870 would be the better option and is reported to be 1 1/2 times faster than the 5770.. Personally have no problems with flashed cards subject to the being supplied by an experienced merchant who offers a warranty. Us a Hd4870 flashed card with 1GB memory with absolutely no problems (touches wood).

Just make sure you Mac Pro as a 3.1 model and not 2.1.

Here is a cheaper flashed option:-


http://www.ebay.com/itm/New-ATI-Rad...rd-Apple-Mac-Pro-/130452024006#ht_5093wt_1398