I don’t want massive boxes like a pb-16, solid extension to 20hz or lower and my listening room is 2000 cubic ft but the left side of it opens up to the rest of basement so maybe a total of 5-6000 cubic ft. My speakers are rp-260f 440c 240s’s n 150m’s for rears
If the usage is mostly movies...even if it weren't I'd still go for the VTF series...The depth extension on the VTF is better and they are just as musical as the ULS series...they might be large, but they're much quicker and tighter than subs of old so imo unless it's a size issue or it's a 100% music system and you won't ever need the extra extension I'd always get a ported sub.
Midbase does favor the ULS series, but I typically like my mains floorstanders picking up mid bass.
I have just south of 2800 cu ft so a similar sized room also opening to other space. I have two VTF3 mk5 in my system and they barely break a sweat...due to localization issues I didn't stay with one sub on the front wall and one nearfield.
I do want a near field sub so I can see a day when I add a 3rd for that purpose (no need for a 4th the way the room is shaped).
You're well on your way to a killer system with four!