You're gonna want to get as much absorption into that room as possible. Obviously, you can't cover up the windows and glass doors with acoustic panels
But what about the wall opposite those windows?
If you check out
GiK Acoustics and
Acoustimac for a great selection of absorption, bass trap and diffusion products.
Both companies offer printed "Art Panels", which are a fantastic way to "hide" absorption panels or bass traps by making them very attractive. Most people like to hang some pictures, posters or art on their walls anyway. So why not "kill two birds with one stone" as it were, and make those pictures out of printed "Art Panels"that can serve a double purpose?
Both also offer a wide selection of fabrics. Acoustimac even offers suede. A great way to keep the cost down is to use smaller panels of different, attractive fabric colors to create your own pattern on the wall.
You will indeed benefit from putting a rug over your floor as well. You don't have to cover the entire floor, or carpet the whole room if you like the look of the hardwood. But at least get an area rug for the portion of the floor that is in between your front speakers and your seat. That's the main spot where you want to reduce the strength of the reflections off of the floor.
Having your speakers sound too "thin" either means a lack of mid-bass and bass, or too much high frequency energy. In this case, I think it's most likely the latter. So absorbing some of the high frequency energy that's bouncing around your room like crazy right now should really help
If, after you've added the rug and as much absorption as you can, you still find the sound unacceptable from your current speakers, then I would suggest that you opt for speakers with a more narrow and focused dispersion pattern. Perhaps a horn-loaded HSU or Klipsch speaker. Or planar or electrostatic speakers.
Hope that helps!
