Preamp or power amp has more impact to resolution?

Thanks for all inputs,
To be honest my system has a bit of strange combination to some.
I am using TW Acoustic Raven with Ortofon AS212 and Lyra Delos for analog front end while digital front end is Sony XA9000ES. My preamp is Audionote M7 and amp is Lavardin A80, speakers is Totem Forrest.

I have talked to some friends and they suggested if I can only change one to increase resolution it would be the preamp.

I read somewhere about wide bandwidth power amp, does it mean that power amp with wide bandwidth will have more resolution?

Wow, seems that I need to change the whole of my system :)
Seems that I have to use my charm to let dealers to show case, see and let my ear to decide.

Thanks again