don't know how/if these facts change your calculus:
(1) that "additional mile/$" at PM (and the additional additional 2 m/$ at DM) only count toward RDM, not MQM
(2) next year the MQD spend thresholds for all levels are going up
Silver -- $3,000 (was $2,500)
Gold -- $6,000 (was $5,000)
Platinum -- $9,000 (was $7,500)
Diamond -- $15,000 (was $12,500)