upgrade

My setup:
pioneer elite sc-05
polk monitor 70 front
Monitor 60 rear
polk cs2 center
Paradigm dsp 3200

I was thinking of getting the Polk RTi8 for fronts. Would that make much of a difference from my 70's? Also, should I put the 60's or 70's as my rear? I am also thinking of upgrading my center. What would be good for that? Thanks
Pioneer sc-07
center-CSi5
fronts-RTi8
Surrounds-Polk FXi A4
sub-Paradigm DSP 3200