On Rel subs: Which are most musical?


It appears that rel makes some of the more musical audiophile quality subwoofers.
My question is which rel model do I go for? I am looking for a sub that isn't too big, is not sloppy but tight, blends in and fills the room with a natural sound that makes it sound as though it's live, in a very articulate realistic sounding system.
For what I am looking for do I look for a big size driver such as 15" or a smaller driver such as a 10" or 8" driver? Does a two driver sub do better than single?
What are the pros and cons between the two?
Does a smaller driver give me tighter bass and a bigger one give me lower and fuller bass?
pedrillo
The key word was "normally". Low frequencies cover quite a range. In any case, those who make speakers with those woofers down under can have them for themselves.
I don't think of subs a musical at all....I use them to correct room resonances, and make mids and highs cleaner/clearer.
The REL ST series of subs that use the AB class amps are the ones to seek out IMHO. Try a Stadium lll with the amp/crossover removed from the enclosure and use the exact same speaker cable as the main speakers use and be prepared for an absolute revelatory experience.

I use MIT Shotgun S3.1 biwire speaker cable from my amp to speakers and use the same from the Stadium lll amp to the sub and a rear placed Strata lll sub for absolutely seemless integration and bottomless extension. One cannot tell the subs are even in operation. 

I do have full ASC tube traps in the room along with golden Sound acoustic disc corner treatment. The soundstage is huge when the recording is such and deep and tight when otherwise. Yes, unconventional but oh so worth it!