Titanium is not an option unless your name is Bill Gates. I spent over $1000 on the two SS 304 bars you see. Titanium would be as much $$$$$ as a new car and I would not be able to use 2" either, it would have to be 2.5" because it is not as strong.
Finding information on the best metals (stainless steel) is not an easy task. Believe me I have tried. It is a function of the tree type (Liriodendron) and there is not much information available on what is the best metal.
I am very interested if you find any information on the subject.