That would be most appreciated, Scott. I went ahead and purchased Universal Sandbox http://universesandbox.com/
and, frankly, even though it didn't solve my problem it's a very cool tool. Every sci-fi author should probably have it. I sent an email to the developer and told him he needs to market it to the sci-fi writing community.
It lacks some obvious tools (like filters...just what I need), but what it lacks, it makes up for in other things. For instance, do you want to watch what happens to the solar system if you increase Mercury's mass to that of the Sun? Or if you insert a spread of Ceres-sized asteroids into Earth-Lunar orbit? THOSE controls are easy and fun to manipulate. There's even a pre-made template "300 Nearest Stars" but no way to drill down into that info. Just a huge rough sphere of stars around the sun.