Nice project, how about self defineable presets
maybe you shuld rename the options selections like this H.264 (AVI),H264 (MP4), H.264 (PSP), XviD (AVI),XviD (MP4) or first the Video Encoder,Audio Encoder and then the Container format that would work for the combination (mencoders restrictions as smart dropdowns) chosen by the user and maybe even make the user aware of the choices he has for a given combination (comon sense decissioning) and then select/editable profiles for the Encoder tools, so something like SUPER but more advanced (and with a cleaner interface)