Do I need to switch out the backplate when I get a new cooler?

I have an antec khuler 620 right now, but its a few years old and they, as well as some other companies, have some new AIO water coolers I want to try. My case doesn't have the slot for me to be able to change the back plate easy however. So I am wondering if it would be possible for me to just keep using the same back plate?  It still has the holes in the right places, and the water cooling heads probably all weigh about the same, so could I  do it or would I need to take my motherboard out of the case?

Depends on what screws the new cooler uses.  It'll probably work, but honestly, taking out the motherboard and replacing the backplate is, what, a 5, MAYBE 10 minute job at most?  Is it really that important to you to save those 5 minutes?

Depends on if I can find the book for my mobo so I can figure out which plug is for the power button.  Still I'm probably going with antec again so it'll probably be the same screws. 

Just google your mb.  The manufacturer will have a pdf manual.  There may also be labels actually on the board it's self.