Rob,
You're right US Air is the only airline that I am signed up with. I will consider signing up with a second one. I will also give a lot of consideration to applying for the Starwood Card. On average I take one big trip out of the country and two small trips in the U.S. each year. I already have the cards previously mentioned plus a B of A Visa and MC. Each time you get a new one or just apply your credit score takes a hit. I'm not sure about adding those from your list.
Thanks again