All the options (aside from an under-seat personal item with your important belongings) are really the same answer: Give them more money. Buying Comfort+ comes with priority boarding (after First but before Sky Priority now). The Delta website allows you to purchase Zone 1 boarding and that would allow you to board with Silver Medallion elites and credit card holders. You can get one of the Delta credit cards for zone1 boarding too, but if you aren't a frequent Delta traveler that isn't particularly cost effective.