A 2nd pair D of good quality will be 4-5 mil. Stutzle and Zub get their raises next season, and DeBrincat will surely be north of 6.4. Then Sanderson will likely be getting 5+ in his next deal in 24-25. And they have to be forward thinking and know that Pinto and Greig will need decent money if they play how we think they can, especially Greig.
Thankfully I'm not a capologist and someone (hopefully not Dorion) will be paid a lot to craft this team going forward.
Edit: I just did some loose Capfriendly team building stuff. Signed DeBrincat for 8M, Pinto for 2.5M, Sokolov and JBD to 950K, Talbot to 3.8M and Holden to 1. My roster was Brady, Tim, Giroux, Cat, Norris, Batherson, Joseph, Greig, Pinto, Jarventie, Kelly, and Sokolov up front, and Chabot, Zub, Sanderson, Zaitsev, Holden, and JBD on the back with Talbot and Forsberg. That team was over 84 mil, aka over next year's 83.5 cap, and that's without the top 4 D they need. And with Sanderson, Greig, JBD, and the 4th line all under a mil.
Now clearly that's a loose thing I put together in 5 minutes but I don't know if they can sign DeBrincat and get a solid top 4 D. In a trade they would be shedding some salary to get their guy but like I said, they have to be cognizant of the raises that Sanderson and Greig will need soon enough. Buying out Zaitsev is 2,833,334 against the cap.