Kim,
Much thanks. It's about what I suspected. I conclude that if (hopefully when) we do decide to go to Mars, we might as well imagine a larger vehicle, such as Zubrin's Ares, but relize that we will be needing to make major infrastructure changes.

My goal is just to have a "feel" for what the REAL cost of a Mars program would be like. I have no actual first hand knowledge, but in my mind assume something like a billion dollars up front and $100 million per year in additional maintenance at KSC. Not cheap, but the per launch cost is acceptable (to me).

For my purposes I am assuming no new pad, but that a launch tower could be rolled out with the booster as in the Saturn 5, and would be at 90 degrees to the current STS tower.

I have my own idea for a 2 ET tank booster running on 12 RS-68's (4 core, 2 boosters of 4 each) that would launch with 7,800,000 lbs thrust. This probably makes me a certified crank, but it would be interesting to know whether something like it could fit.