Your budget is unnecessarily high; give me $300CAD to work with and I'd be able to scoop at least six interesting typewriters, albeit with a measure of patience. If you want a workhorse to compliment your SM3 then you need a SG1. Full stop. Of course there are a seemingly endless number of makes and models to choose from, so the more specific your search criteria is the easier it would be to pair you with the ideal machine.

Look for one of the so-called "speedline" (4-series -- serial # begins with 4) Smith-Corona portables from the 1930s/1940s, whether the Clipper, Sterling, or Silent (going from fewer features to more features). I find these to be really handsome machines, and they are very fine typers also. Smith-Coronas are also very well made, I find. The 5 series versions of these machines, which were made throughout the '50s, are excellent too, but not as stylish.

There's also the Underwood Finger-Flite Champion and similar models (I'm blanking on the names), which have a really remarkable shape -- very much in keeping with American cars of the same era (early 50s). Good typers as well.

Finally, the Royal Quiet De Luxe and Arrow of 1948-49 were the child of the great industrial designer Henry Dreyfus -- handsome and angular, they were a big change from Royal's more rounded earlier machines. The Dreyfus design got revised and watered down some starting in about 1950, and aren't as esthetically pleasing, in my view. But all of the Royal portables of the '40s and '50s are excellent mechanically, and very nice to use.