Totem Storm vs ?

You won't get anything in that small of a form factor from hsu or svs. But just about anything from those two companies in that price range will be a significant step up in performance. Depending on the music you listen to and how loud you enjoy it, you may not notice those increases in performance. If you do any movie watching though, you will definitely notice an upgrade going with hsu or svs even at low volumes (simply because that totem sub will not go very much below 25hz).

Your mains would almost rival that sub with enough amp thrown at them.
They show two 7 1/2 woofers for your mains at -6 db at 30Hz while that sub shows -2db at 28 it would be little to no gain.

Except for barrier gain due to optimal placement of the mains for imagine not being optimal for bass bla bla blah

Would you get the sub in question for your room with those mains ?

Very fair question. NO.

Those particular speakers deserve a great amp (or amps) and if I felt I still wanted reinforcement below 30hz for a 2ch music only system I'd consider REL's Stentor iii.

I must have just been sleepy -aka cranky.