Well, if you're up to some work...
For the wrapper you can use instead of plain width:
max-width:1100px;
min-width:1000px;
This means that it will not become wider than 1100px, even if someone has a wall-to-wall monitor, and it will not shrink below 1000px wide. Those with smaller monitors than 1024 x 768 will still have to scroll sideways. You can of course set the min-width lower.
BUT:
This is not quite without problems, as
1. It seems that IE does not understand 'min-width' so if someone narrows down the viewport to say just 50px, they may do that.
2. It will have impact on a lot of your graphics. If e.g. the header is wider than 1000px, it will pop out of the wrapper.
3. It will also play its trick on the menu, which will wrap to fit into the 1000px space.
4. It may also ruin the look of any floats you may have (I haven't checked all your pages), which will have to be redimensioned.
This is what I can think of. I don't know if someone else has a better idea for you.