Five-Way NVIDIA GeForce Comparison On Nouveau
Until the re-clocking situation is sorted out so the GPU core/memory/shader clocks are being maxed out as they are rated to do, the older NVIDIA GeForce graphics cards are commonly working better than the newer hardware with this Linux graphics driver.
More of the same... the 9800GTX can slaughter the GTX 680 and the GTX 460 is running at comparable speeds to the very cheap 8400GS graphics card.