It's hard to explain the process of compression since it's tied into your settings in general.

Your video card and .cfg file have to be set-up  correctly to fully use any editing program

I fly in 1600x1200 which I reduce to 800x600 for this site. I than use around 30% compression in ACDsee for complicated scenery shots such as these. That generally puts me under 100KB.

There are different types of compression I use Lancross which gives me good reproduction at lower compression values.

When you save the file you are given options before you do a final save. It is in the options that you can set your % and type of compression.

I have to point out that I use many different color correction settings on my video card to achieve different effects so there is no editing necessary.

My best advise is to study the color correction possibilities on your video card's control panel to see what is possible.

I ended up having to use 39% compression for some of my shots even after resized to 800x600.  I was using the same compression method as yourself, I found that one gave the best results when I compared them all.

Now to work out these colour correction things  

Just had a quick play.  You gotta be very careful how much you move that line!  I had my screen going all sorts of weird colours    I might take a few screenies of it flurescent style seeing as I technically haven't edited it lol.  Just to work out which way to move the line is the tricky bit I am guessing.

So what does all that eye-candy do to your framrates (ps...I do plan to use FS-GS, but I am in a bit of a transition right now, so I have put it off for the time being)...

Just amazing.