Here's a crop from an image I'm halfway through. As you can see there is a marked difference in color quality after color conversion. My question is: is it possible to get the image close to the RGB version again using the color balance or hue/saturation functions....I've started playing around with that but the results look kind of nasty so far.

Thanxz. Although come to think of it as I type this, the cmyk version might look better!

Try increasing the pictures saturation, or the contrast. Try tweaking some things in the image options menu.

using your colour balance, curves, hue/saturation, and brightness/contrast, you should be able to get it to look right again. t'is a tricky mofo it is. If you don't tend to use RGB only functions, such as certain filters etc, you may as well start all your files in CMYK from the start bro...