You want to use airberlin from JFK to Berlin (Avios partner) because there are NO taxes to pay ($2 on a one-way). That compares to over $500 of taxes on the BA flight. Flat bed seats, food is not great but is acceptable.

I'm sure you can get from Atlanta to New York easily enough.

I wrote a big article about using airberlin here if interested - http://www.headforpoints.com/2013/11...-on-airberlin/