Saw a B&K AVR 507 for sale would this be a decent up grade from a Yamaha RX-V2400?
What can it do that your Yamaha cannot do that you need it to do? If nothing, then absolutely it is not worth it to get it. Many times, people spend their money upgrading to something that is better on paper, but makes no practical difference in their particular system.
As for amplification, if you need more robust amplification, you should be looking at power amps, which you will also be able to use with your next receiver when you upgrade to get some of the features available on newer models. But if you do not need better amplification for your particular speakers, then do not waste your money on it.