Well, Actually you did they way I would have done it.

I mean, the AVI renderer doesn´t seem to output a good image, so I guess the best way to render a good animation would be to render those images separately and then assemble them in Premiere © or whatever. As a matter of fact, if you want a really good picture and handling of everything you can even render them in layers -along with alpha channels- (such as reflections layers, shadows layers, etc) and then play with those when compositing.