What is it that you are not happy with? You should make a list of what it is that you think needs improvement. Is the room carpeted, drywall, ceiling tiles, what furniture, etc...
Additionally, how far apart are the speakers? You say you are 12 feet away.....you should be equa distant from the speakers as they are apart.....equilateral triangle. Are speakers toed in at all? Makes a big difference....are they on stands or floor standing? What kind of music? Do they sound good or great with just some genres? Are you using any kind of power conditioning? So many questions that need to be answered before you throw money at it.