I have the QTsi as well as the Maxium 70. I have the minolta 70-210 zoom lense which has worked very well for the four years I have had it. They now have a 75-300 zoom lense which is fairly inexpensive but very good. It would be an awsome lense. There is also the option of the 100-400 but that one tends to be a little slow. Sigma/Tokina/Tamron lenses are all fairly good lenses while being reasonably priced, so don't rule them out.