Well, the HSU speakers may sound great at lower volume levels as well. You may want to try asking owners of these speakers in an owners thread at this forum or other forums.
But it would be hard to fault you for picking up the Ascends. And I understand your point regarding your small space. That is why I recommend the smaller and less inexpensive HSU sub. Anything larger could be overkill.
Does your apartment have concrete walls? I have this vision of a room with sliding wood walls layered with rice paper