Good luck with your seedlings, DJ. I have my fingers crossed for you. I like that this is something you are working on. It seems it's easy to get caught up in the latest hot trend, but I like to think I can dedicate 20-25% of my seedling space to trying to improve June and September color in my garden, and still work on lots of "pretty faces". Keep an eye on the September and October seedling postings, and if you see me post something of interest, let me know. I didn't post much this year, but I did in previous years, and will try to do better next year.
At some point, I'll try to remember to look at my older stats to see what reblooms here in September regularly, but zone 5 isn't zone 3, for sure. Based on this year, if you don't have them, VL Genesta and rebloomers May May and Bitsy seem to be OK with the cold. I also have a NOID that was sold as Purple de Oro, but isn't purple, that didn't slow down with the first frosts.
Sold as Purple de Oro, if you see it somewhere. It went really cold this year. For sure my last bloom in October.