GeForce 7800 GTX... the best card for a PCIe G5 Power Mac?

I have started out on the rocky road to upgrade the graphics card on my Power Mac G5 Quad 2.5GHz running Mac OS X 10.5.8. The standard card, a GeForce 6600, does not do justice to this wonderful computer, and struggles with any serious video work.

The first step is easy – deciding on the best card. A little Googling shows that the GeForce 7800 GTX wins hands down over the competition.

The next needs patience – these cards appear from time to time on eBay; I will need a 512 MB PCI-e version (not 256 MB) as I am running 10.5.

I've waited a month or two, put in a winning bid and the card has arrived. Now all I need is the code to flash the ROM to make it work in myG5. Not so fast! I'll need a 128kb ROM chip! The idea of using a soldering iron terrifies me, so I'll have to find someone, who does this sort of thing for a living, to remove the 64kb ROM from my 7800 GTX and solder on a 128kb ROM.

But what's is the right spec/manufacturer/supplier for the 128 kb ROM?

IfI am lucky my friend with the soldering iron may know. If not, I'm stuck. I've not been able to find this information anywhere on the Internet.

Now all I need is the right code for the ROM. It seems that there are two versions that people have used: one, which seems quite common, is lightly edited Quadro FX 4500 ROM code which does not use the full power of the 7800 GTX, which after flashing reports itself as a FX 4500; the other, which seems to be as rare as gold dust, has been fine-tuned to use the 7800 GTXs full potential. Cards flashed with this version report correctly as 7800 GTX. I really want this optimised code, but neither version is available from any of the usual places.

Can anyone please help?