Delta lays it out clearly (see below). Only if you charge $25k on the current cards you have/are considering does it help you.
https://www.delta.com/content/www/en...s.htmlPriority

As Silver you're not likely to get upgrades at all, so probably doesn't really change much even if you had the Reserve Card.

Complimentary Upgrade Hierarchy
1 Medallion Status
2 Fare Class Groupings: higher-priced fares are ranked above lower-priced fares
3 Delta Reserve Credit Card Members
4 Delta Corporate Travelers*
5 Card Members who earned the Medallion Qualification Dollars (MQD) Waiver in the current calendar year1
6 Date and time of upgrade request