I'd probably get him the EF-S 55-250mm f/4-5.6 IS or the EF 75-300mm f/4-5.6, just looking at Canon's site and seeing what lenses they have. Both of those lenses are reasonably priced by the looks of things, and I know I use my Nikkor 55-200mm way more than I ever used my 18-55mm. I love my 50mm f/1.4 as well, but I'm glad I got my 55-200mm first.