The Windows benchmarks for the NVIDIA GeForce 9600GT put it ahead of the Radeon HD 3850 and Radeon HD 3870 graphics cards. In fact, in some benchmarks it's quite far ahead of these two mid-range AMD GPUs. However, that isn't what we exactly experienced under Linux. In Doom 3 and Enemy Territory: Quake Wars the Radeon HD 3850/3870 had pulled far ahead of the GeForce 9600GT when running at both the NVIDIA and ASUS stock speeds. In Quake 4, however, the NVIDIA graphics cards had the upper-hand (likely due to a regression with the Catalyst Linux driver). Unfortunately, these are the only consumer options for Linux tests due to the lack of native Linux games. NVIDIA's older mid-range graphics card, the GeForce 8600GTS, had performed similar to the 9600GT, but the G94 had pulled ahead in the demanding situations.
When it came to the 2D GTK performance, the NVIDIA graphics cards were much faster (aside from GtkComboBox and GtkTextView) due to their recent XRender improvements. Meanwhile, AMD is working on implementing Textured XRendering, but that is currently disabled by default, which leaves AMD's Linux driver much slower in GtkPerf tests.
Back when the GeForce 8 series was originally introduced, NVIDIA had a Linux performance problem (and other issues) with these graphics cards, similar to what we experienced today with the Radeon HD 3850/3870 pulling in front of the GeForce 9600GT. We had found this out when comparing the GeForce 8 Linux and Windows drivers. A number of driver releases later, NVIDIA had corrected this problem for the GeForce 8 series on Linux. We believe NVIDIA has another mighty performance issue on their hands with the GeForce 9600GT -- even though the GeForce 9 series is just a minor revision to the GeForce 8 family. NVIDIA has yet to officially confirm this information.
While we have faith that NVIDIA will be able to correct this performance problem in a timely fashion, for now the GeForce 9600GT isn't leading the mid-range graphics card race on Linux. In only Quake 4 did the 9600GT have the upper hand and that's likely due to a regression with the recent work done to the proprietary AMD Linux driver. If you are looking to invest in a mid-range graphics card for the long run, you may want to wait it out until NVIDIA addresses this problem and see what they decide in regards to a counterattack against AMD's open-source graphics strategy. For those dual booting to Windows for gaming and using Linux for all other tasks, the GeForce 9600GT may suit you well. However, like the GeForce 8 series, the GeForce 9 series doesn't support XvMC (X-Video Motion Compensation) for video playback. NVIDIA also has yet to support PureVideo HD under Linux.
Speaking specifically to the EN9600GT TOP graphics card, ASUS has done an excellent job with their choices surrounding this GeForce 9600GT graphics card. The card comes factory overclocked with heightened core and memory frequencies and we were able to push it even further to achieve a rather nice overclock. The Glaciator Fansink is an excellent graphics card cooler and was quiet during operation while the GPU die temperature was quite low compared to the reported numbers for the G94 reference cooler. The ASUS 9600GT also includes a DVI to HDMI adapter and audio pass-through support, which is another plus. For those looking for DisplayPort support, however, ASUS currently doesn't have a 9600GT solution. The ASUS EN9600GT TOP is currently available for $170 USD, which is priced appropriately and will be a great solution for Linux users if NVIDIA is able to work out these driver shortcomings.