I wouldn't do the "T". Bryan nailed it on the head. Water is just like electricity. I wouldn't do a pump either because you could never match the pressure from one rad to the next. You could end up with a circular flow from rad to rad. Unlikely, but I think you get the picture.
Unless it was the exact same rad, same condition, and the same length of pipe from the T and back to the T on the outlet.
Have you considered running them in series?