I fly frequently from US to different regions of Europe, the one thing I learned is if you are not flying first class, just get the ticket with cheapest fare

It really doesn't matter much in terms of quality of the service, etc; but your baggage is heavier than usual. Prepare to pay more, IF they agree to take it on the plane. I am not sure, but I guess the limit should be around 90 lbs (ask the agency or check with the company).
One other thing, take the bass with you to the plane. The planes fly internationally have bigger compartments, those will accomodate a bass in hardcase.