so the gto is an ATI x800 or x1600. I am confused about the difference and what performance increase in Second life I could get.
The GTO is the X800 that Raven linked to.
Pretty much whatever the APP the X800GTO or GF6800GS would be better than both the X1600Pro and GF6600GT.
Second life does not have benchmarks posted that I could find but looks very vertex heavy so you'd want those other cards for their heavy vertex/geometry engine power. However depending on the engine it may be more CPU bound, since the developers don't seem to recommend classes of cards so much as memory levels.