Hey greek, have you considered using an expanadable layout? If you use tables, you could set the width to 100% or 90% or something. This would fill up the entire screen, regardless of how big the monitor is. If you use a fixed width greater than 750 (i.e. if you use 1000, like you are considering), then you risk annoying those people who have smaller monitors. I absolutely hate it when I have to scroll horizontally to read a page.
If you look at this page (near the middle of the page), you will notice that 25% of the population still uses a screen size of 600 x 800. The number is shrinking each year, but I don’t think I would design a site without taking this 25% into account. If 25% of your visitors leave your site immediately because it’s too hard to use, you could stand to lose a lot of money….
My 2 cents.