800x600 is dead, with less than 2% of all internet users running at that resolution. 1024x768 is the new standard. So a width around 960 or above is perfect. Google for the 960 grid system or go to
http://960.gs - 960 grids have been all the rage this past year.
Don't worry about 800x600 resolutions.
Btw, I have a macbook pro, and I run @ 1440x900 Ashley :p.