Overclocking will not void the warranty. My Sapphire X800GTO2 came with overclocking software endorsed by Sapphire. When I installed, it said nothing about voiding the warranty. It has an auto-overclocking feature which attempts to find the highest overclock for your card. It's an OK program, but ATI Tray Tools is much better.
X800GTOs almost always come with 16 pipes enabled now, so old "stock" benchmarks should be updated.
Notes on the overclocking software and card in general:
http://www.techzine.nl/extreviews/6632
X800GTOs almost always come with 16 pipes enabled now, so old "stock" benchmarks should be updated.
Notes on the overclocking software and card in general:
http://www.techzine.nl/extreviews/6632