[Nuance]

How big is your room?  The room will literally destroy a subwoofer's in-room response (output) if it isn't placed properly or if the subwoofer is too small for the cu. ft. of said room.  Can you provide your room dimensions (L x W x H)?  Before pulling the trigger you (we) need to make sure you're purchasing enough subwoofer for your room.
Nuance, the room is divided by small partition.  The listening area part is 10ft wide by 20ft deep x 10ft high.  The total room size including the room on the other side of partition is more like 25ft wide  x 20f deep x 10-14 ft high ( the ceiling height in the other side  of listening area is 14ft).
 So it,s hard to say whether to measure the listening area only or the total space, esp since the partition is partial. Does this make sense? It,s an odd space.

Thanks
Tom

Unless the partition seals in the room (sounds like it doesn't) you have to count the entire space; bass doesn't care if there is a partition unless it's it's own sealed in space.  So based on that your room is 7000 cu. ft. using the 25x20x14 measurements; that's a huge space to fill!  With that said, get the biggest subwoofer you can afford!  The Rythmik F15 will certainly be better than the 12, but even that won't pressurize the room in my opinion.  I guess it all depends on what kind of performance you're looking for.