JPEG Compression Limits

[Tom C]

I've been trying to get my PUG entry finished and when getting to the last 
step of saving it as a .jpg, the smallest I can compress the file is 102K, 
at Photoshop quality level of zero.  This is for an image that is 600 * 394 
pixels, resampled at 72 ppi.  There is noticieable degradation in the image.

The smallest I can compress the image at it's physical pixel size, and still 
get reasonably good results yields a filesize of 134K at Photoshop quality 
level 3.

Any suggestions or have I simply hit the compression wall?  The image is a 
silohuetted trees with fairly open branches and therefore, I assume, has 
quite a bit of image info compared to shots that may have large contiguous 
blocks of color (assuming again I have an inkling of how jpeg compression 
works).

Tom C.