Try Iris, its an extraordinarily powerful program, but with a quirky interface, and it's free.
http://www.astrosurf.com/buil/us/iris/iris.htm
If you have some dollars budgeted I would suggest ImagesPlus from:
http://www.mlunsold.com/
It is very easy to use, and deceptively powerful. Makes it easy to get nice results. Arguably ot as good as if you are a Photoshop expert, but I'm not so I like it!
FWIW
Gary