One of my favorite street kits includes a zoom, a prime, and yes, a 2X teleconverter. That last item might seem out of place. Many photographers use teleconverters only when they have to, and that's usually with longer telephotos.
Me, on the other hand, use mine primarily with a Zeiss 50mm f/1.7 prime. And here's why.
Over the course of a long day that drifts into evening, my lens needs change. While the sun is out, I tend to rely on zooms, such as the Zeiss 35-70mm f/3.4. I like being able to frame the shot to my liking before it disappears (which happens quickly in street photography).
When the light begins to dim, however, I rely more on the fast 50mm at wide apertures to allow me to continue shooting without supplemental flash. I love fast 50s, always have.
But I also like the 100mm mild-telephoto range, especially for portraits. So instead of carrying my slightly-bulky 135mm f/2.8, I find myself packing the much smaller and lighter Mutar 2X teleconverter and using it with the 50mm.
With the teleconverter paired to the 50mm f/1.7, I get the reach that I want (100mm), and a still reasonable maximum aperture (~ f/3.4). Most importantly, the shots look terrific.
I know some folks shy away from teleconverters because of the perceived compromise to image quality. But my experience has been that's only with inexpensive, unmatched 3rd party optics. When I use my matched Zeiss or Canon teleconverters, the pictures look great.
So if you want to travel light, but still add a bit of reach to your street kit, consider a 2X teleconverter. I seldom leave home without mine.