Thanks folks, all of these are helpful.
However, we've tried XV and ImageMagik and they don't seem to like our AIX box. It appears that we are missing a compiler.
We're trying something called EasyCopy which has a conversion feature that might be worth it. Also, on the Windows side we're trying ReaConverter Pro which seems to do the trick and then some. Very fast, too.
Now if I only had a way to create the metrics I need on the AIX box....
I'll keep everyone posted.