No you don't need a cap, they don't work for what you're thinking.
Yes, you could probably use a Big 3 upgrade.
No, you probably aren't pushing "1125 out of the amp".
I don't see any Dayton's fitting my needs on there. I saw a pair of no-names, Pyramids, and PRV Audio. Those were the only 3 I could find. Maybe I'm looking in the wrong place?