Have you tried Devonthink ? It is a very powerful information manager surpassing any other product like on Mac or PC. Version 2 is apparently underworks should be available soon. Not to draw business away from the good folks at omnifocus but it can be purchased as part of the give good food to your mac bundle that ends this weekend (
http://www.givegoodfood2yourmac.com/store/) or from the developers website (
http://www.devon-technologies.com).
As I have posted elsewhere I think that there could be a niche for an Omni product that competes with the lighter weight filer organizers such as Together, Yojimbo, Eaglefiler, etc.