Room is way too bright.

My primary listenings system is in a room that also has a projection TV.  I solved both issues in regard to the one wall that is floor to ceiling windows by having some acoustic curtains made up that both make the room dark for viewing and damp reflections for listening.

Dipoles. Or do what I did but your room is going to be very very dark. 

Without knowing the layout of your room there have been a lot of good suggestions.  Depending on the number of windows, covering them properly can get expensive.  If you have hardwood or some other hard surface for the floor, get a large rug in front of the speakers.  Also treat the first reflection points if they can be attached to a wall.  There are also portable absorption treatments on stands if a window is at the reflection point.

Make your own acoustic treatments. Anyone can make them, and make them look professional. Very cheap to make and even customize.

I have used sound absorption panels from a company called ATS acoustics, and you can hang them from your windows temporarily while listening and take them down when you’re done that might help.