I currently run Sierra-1 NrT with a Rythmik f12 sub. Sound is great, BUT, could it be better?

I never turn up the volume to levels where speakers are really getting a workout but if there is a real difference someone heard after upgrading from Sierra-1 to Towers, it would be great to hear your thoughts.

I have a dedicated home theater with light acoustical treatment. Room is 22 x 14 approximately.