I just bought Focus XD three months ago. Their bass is just out of this world. Best bass I have ever experienced in my audiophile life for over 30 years. I had Thiel CS7.2, Revel Salon 2, Alon Exotica with Thunderbolt sub before. But the Focus XD blew them all away in the bass department. My room is 25x14 feet with 14 feet vaulted ceiling, and also an opening in the left to the kitchen behind my listening chair. My room is very similar to yours. Legacy is famous for great bass. I am very confused with your situation. However, XD has an internal amp for the bass. I use external amps for the mids and highs. Signature SE should provide plenty of bass even though it doesn't have an internal amps.
My Focus XD is 7.5 feet apart, 7 feet away from back wall and I am sitting about 10 feet from the speakers. I have Conrad Johnson preamp that inverts phase. I have to invert phase again at the speaker terminal. If I didn't do that, bass was absent.
You don't need break-in. Bass was awesome from day one. Signature SE is 4 ohm. Legacy used to use Coda amps for their demos at shows. So Coda should not be a problem. I don't know Coda. Is it configured to drive 4 ohm? You said your speakers are only one foot from back wall? If so, it should have plenty of bass since it is sealed.