I think that because he's new, you're not quite seeing the "real" Duncan yet. That's great that he came out tonight. Robin goes in and out of his cage, but I do find him inside a lot.
For now, just let him come out when he wants to. Eventually though, you'll need to get him out at times. Find out what his favorite treats are, and see if you can entice him to step up from inside the cage by offering a treat. Another thing that might prove handy is a stick to step up on. Especially when he's hormonal (and since you say he's cage territorial) it's a good idea for him to be stick trained to save your fingers when you might need to take him out at a certain time (to go to the vet, to give meds, etc). My Pois aren't cage territorial, but my Pionus is really bad.