Lower file sizes with the same size upload don't translate into too much degradation on the web..at least the sizes I post.  For forum, an 800 x 600 shot is large enough without introducing much scrolling for the viewer and can easily go to less than 200kb and be fine for viewing.

When a pic is so large it cannot be viewed in the screen of the monitor, scrolling takes bite out of the impact.   So, size to 800 to 900 wide is my suggestion. Panoramas are a different breed and we expect to scroll to see those.    Just my 3 cents worth.       TomDart.