Preamp or power amp has more impact to resolution?

Over many years, my experience has been the priority ranking is Linestage first, then Power Amp, then Phono stage. Obviously you don't want to get too far out of balance by, for example, pairing an entry level power amp with a top-of-the-line linestage, but in general the linestage seems to have the greatest impact on overall sound quality. I have had a number of phono stages and power amps that I find quite good sounding, but very few linestages that I have actually liked.

Well said Salectric - that is my conclusion as well on all points.

...which upgrade that can provide more impact...

... at the end of day: the Quality of your Speaker Drivers and the sensitivity after
the X-over

speaker upgrade...

you could also add, do consider the integrity of the designer and builder of your prospective speaker.

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