Based on the culture and wealth of the cities, I would rank NYC, San Francisco, Austin, TX, and Seattle at the top. I don't know enough about places like Chicago and LA to rank them. I would love to see Amira in Seattle. I also think Ted is right about Vancouver, BC. I'll bet that Amira could fill a big hall in any one of those cities.
Edit: two more: Boston, MA and San Jose, CA (Silicon Valley).
I am being very careful here since classical music is not strongly supported in the US. So I am looking for large urban populations of well-educated people with disposable income. I think this gives the greatest chance of success. Florida also makes sense, because of the large population of well-educated retirees there, many with strong European roots. Amira, if you visit anywhere on the west coast, please visit the beautiful national parks. You will love it.