Here's an online link:
http://www.dewclawarchery.com/Kinetic_Engery_Calculator-a/157.htmAnd if you have a pocket protector and a Hewlett Packard handy:
The kinetic energy formula is:
1/2 Mass times velocity squared
or
Kinetic Energy = (1/2 M) x (V2)
I'd agree with the cam comment above, and the other advantage with the new bows is weight reduction and riser design. I still have a Golden Eagle Hunter that I break out once in a while as a reminder of what will kill deer, and what advantages a new bow has. My Hunter still works, if your bow is still working for you, no need to change unless you find a design or feature that really appeals to you.
Best advice I could suggest is to go shoot every bow you can in your local bow shop, and see if any really give you an advantage/gain over your current set-up.