Dunno why you posted it twice. Anyway, the GTO is only avaible OEM, is PCI-express only, and isn't a very good card for its price. I would suggest getting an X800XT or a 6800Ultra (both are very viable cards). They are top-of-the-line right now and cost about 500 bucks each.
There are also "more powerful" versions of those cards, the X800XT Platinum Edition and the 6800Ultra Extreme, both costing about 700 bucks and very hard to find, not worth it in my opinion.
So whether you get the nVidia card or the ATI card is up to you, they are both very close.
Other cheaper but still good cards include:
6800GT or X800Pro for 400 bucks
6600GT or 9800Pro for 200 - 300
6600GT (PCIe) or X700Pro (PCIe) for about 200