With a suspended floor the best thing to have under the sub is a concrete patio slab. Heavy is good. Even a 2" thick two foot round one is 70 pounds. But bigger would be better.
With a heavy slab under the sub, the floor will be less of an issue, and the sound will travel through the whole home less too.
The slab can be on anything like a throw rug to protect the floor. then spike the sub to the slab. You can paint the slab to hid it a bit.
As for in another room, that would depend on the sound, and if you can integrate the sound into the system that way good enough for your tastes.
With a heavy slab under the sub, the floor will be less of an issue, and the sound will travel through the whole home less too.
The slab can be on anything like a throw rug to protect the floor. then spike the sub to the slab. You can paint the slab to hid it a bit.
As for in another room, that would depend on the sound, and if you can integrate the sound into the system that way good enough for your tastes.