Place the speakers and sub woofer as in the image.

- spksub.jpg (36.93 KiB) Viewed 4506 times
As a solution for dust on sub woofer, use a polyethylene cover when you are not using it. However you won't care much about dust as time goes on
I see another problem. Your current mouse position is not correct. It must give you a huge pain on your wrist after some time. If there is no mouse tray on the keyboard, you can either fix on or keep the keyboard to a side and place mouse there.
See following images.
Correct sitting position:

- km.jpg (20.55 KiB) Viewed 4504 times
Correct keyboard and mouse position:

- k.jpg (13.94 KiB) Viewed 4504 times
Mouse placed too far from the body: A keyboard or mouse that is not directly in front of or close to the body forces the person to repeatedly reach during use.

- w1.jpg (23.75 KiB) Viewed 4504 times
Some good points:
- Make sure the keyboard is placed directly in front of the user.
- The mouse should be positioned at the operator's side with his or her arm close to the body. A straight line should be maintained between the hand and the forearm. The upper arm should not be elevated or extended while using the mouse. The employee should not have to reach to use the mouse.

- w2.jpg (24.03 KiB) Viewed 4504 times
- Consider using a mouse platform that rotates above the keyboard while maintaining about the same plane. This design allows the mouse to be used above the 10-key pad, which gives the user a better wrist angle and reduces reach.
The proper position of the keyboard and mouse is essential in creating a comfortable workstation. Consideration of those factors can help prevent musculoskeletal disorders such as
carpal tunnel syndrome and
tendonitis.