The little Hsu is a really good little subwoofer and should be able to handle 2500cuft at medium volumes. Because it's a vented sub (and a Hsu) it'll reach its full fated 25hz and it should be really easy to setup. However because it's a downfiring sub having an appropriately sized subwoofer
isolation pad under it is a must to keep the downstairs neighbors happy. For roughly the same price (with shipping factored in) the slightly larger
Elemental Designs A2-300 is a bit more capable but eD usually has a bit of a wait - always confirm ETA when shopping eD. You'll also need a bit larger
pad to go with the A2-300.
The sealed Emotivas are a whole different animal. They are much smaller with a very-very detailed sound but as Buford stated without a bass port they naturally want to roll off pretty high. The designers use built in eq circuitry and raw horsepower to keep the frequency response flat down to ~30 (Ultra 12) where it falls off quickly. Sealed subs rely on the room itself and placement to boost low frequencies. I haven't heard an Ultra 10 but I own an Ultra 12 and IMO a sealed 10" might struggle in a room that size and the Ultra 12 digs a tiny bit deeper. If you go sealed you'll want to place the sub carefully to take advantage of room gain.
What to choose? If you were a big action movie watcher in a house then a big ground pounding vented sub would be a no brainer. If the use is 90% music the answer would be simple
if your taste were jazz, classical, and/or classic rock - the Ultra 12 because those genres have little or no energy below 35-40hz and both jazz and classical have a lot of detail in the bass. Electronic dance style music (techno, house, etc) can hit those pounding 20hz notes but have little or no detail to the bass. You'll have to figure out
your priorities.