The only important number is the main part number FDA24N40F; the other numbers (top line) is the batch / date codes and not important while sourcing replacements.
However, you do need to install all matching MOSFETs per bank (all must have the same batch / date code).
Typically if only one or two FET's are blown you replace ALL of them, even if the output stage uses 16. You can sometimes get away with replacing all of them in one bank and leaving the rest alone, but I feel more confident replacing them ALL and is what I do. Don't skimp or it's gonna blow again and will be a crappy repair.
Also do NOT buy them on ebay or any other non reputable part distributor (a lot of fake / counterfeit parts on there), the price seems cheap, but when the amp goes up in smoke again and takes out the power supply FET's you'll be sorry you went the cheap route!
You can't go wrong with Mouser or Digikey:
Mouser has them in stock: http://www.mouser.com/ProductDetail/...G%2FX4wA%3D%3D
Don't forget to check the gate resistors as they often open up when FETs blow, and the drivers; you miss something there and it may blow as soon as you power it up, you may already know all this, but since your asking about FET's you may not...