Currently, I use my Harman Kardon SoundSticks 4 as my living-room speakers with the aux input connected to my AirPort Express (2nd Gen). The AirPort Express provides reasonable audio quality and streaming support for my Apple devices. When I listened to the SoundSticks, I noticed that they sounded quite boomy at normal listening volumes: an EQ was being applied that would increase the bass at low-medium volumes, probably to counteract the human equal-loudness contour. I was able to mitigate this by manually increasing the volume of the SoundSticks and lowering the volume from AirPlay devices.

Since there is no AirPlay support in Windows, my PC must connect to the speakers using Bluetooth. Any changes to the volume on Windows directly controls the volume of the SoundSticks, meaning we have the problem of obnoxious bass at low volumes again. Fortunately, there is a registry hack in Windows to disable the physical volume control of Bluetooth devices and use software-based control:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Bluetooth\Audio\AVRCP\CT]
"DisableAbsoluteVolume"=dword:00000001

Overall, this provides a pleasant audio experience in Windows without any changes to the physical volume of the SoundSticks!