The only real advantage I see in any of the above are the wide and possibly fisheye lenses. The tele-converter would basically be useless as lengthening the focal length of your lens would not be of great benefit. You probably lose a stop or two, and a longer focal length means that you're further away from your subject when filling the frame as opposed to a shorter focal length. If you're further away, the quality of light is lower as the light travels through more water (and is more filtered). As well, with more water between the subject and the camera, there can be more particulate matter present.
Now as far as the wide angle lenses, yes, absolutely. In general, this allow you to get closer to your subject and reduce the amount of water between the camera and the subject. This = good. But what you have to check out is that the lenses work with your housing and camera. There can be vignetting that can occur, and with wide angle lenses sometimes there can be softness around the edge of the image. You need to make sure that if any of this is present, it is acceptable to you, so make sure you get the proper lens. I have the same system as you, and I use an INON UWL-100 type II, which works fine. There's a little vignetting, and some softness around the edges of the images, but I zoom in just a touch and all is good.
