We decided to name the new little kitty Arthur (as in Sir. Arthur), and he and Tofu seem to be getting along purrr-fectly! They no longer growl or hiss, and enjoy playing tag and chasing each other around the house (I'll post a video soon). They even share food and water without any squabbles. :)
Arthur did very well at the vet on Monday, and purred the whole time. He's currently being treated for hookworms and got all the necessary shots, but otherwise is as healthy as we could have hope for! Woohoo!!!