Hi Goose,
Have you considered acoustic treatments on wheels that you can move in front of the windows during listening sessions and then pushed off to the side afterwards? The do-it-yourself route is the cheapest and I would suggest you consider curving some thin plywood into polyfusers, which shouldn't be too hard or costly.
If your bass traps are fiberglass filled, then I might suggest you pull them out from the wall to leave an air space, or rotate them 180 degrees to create the air space. You might consider putting two of them together to create a rectangle and thus thicker trap that works to lower frequencies. With so many large windows, the lowest frequencies will exit via the wondows so you're likely concerned with upper and mid bass frequencies. Also, the absorption panels should be about 6" thick, not 2", so that they work across a wider frequency spectrum. Thin absorbers act as a low pass filter and skew the freq response of the reflections striking them thereby changing the timber of your cherished speakers.
Try and deal with front and back wall reflections first as they're less advantageous. You will want something thick to deal with the back wall reflections including placing them in front of the window. Polyfusers would be a neat thing to try behind your seat.
Good luck.
