I suppose it's a matter of opinion where one draws the line between upper-tier and mid-tier. For SQ, the hierarchy of status is:

Lifetime PPS Solitaire
PPS Solitaire
PPS
KF Gold
*A Gold
KF Silver
*A Silver
KF Member

Within the PPS levels, SQ ranks members by the number of years that status has been held. In other words, QPP4 (fourth year as a PPS member) outranks QPP3 (third year as a PPS member).

I would consider PPS and higher to be upper-tier, KF Gold and *A Gold to be mid-tier, and KF Silver and *A Silver to be lower-tier. Slice and dice as you see fit.