See my signature for another program that, even at this early beta stage, whips the pants off everyone for rapid view-by-whatever.
Whatever you decide, DO NOT repeat DO NOT EVEN THINK ABOUT resorting outside of the iPhoto Library. It is specifically constructed by Apple to resist this, and attempting to do so will usually result in lost data and a corrupted library.
You can resort within iPhoto by size, which should give something approximating what you want, and the program I mentioned before (see my signature) can create a catalog from iPhoto's Library so you can resort to your heart's content WITHOUT messing up iPhoto, so again you may want to have a look.