Sonic advantages krell fpb 400cx/700cx.

Hi all.
As for now im feeding my dynaudios c4 with a kps 25sc thru a krell Fpb 400cx,im in to upgrade to a fpb 700cx,so my question is,what sonic advantages can i expect?If any.
Why do you feel the need to upgrade ?

What is wrong with the amp you have now ?
Ohh,nothing wrong with the amp i have, but i am just curious what i can achieve with the 700 cx.Been reading a lot of positiv reviews about this amp.
i would get monos vs the 700cx because of sheer size.