Regular headphones have a larger size jack than the headset jack on the 8100. Also, even if you get an adapter that fits the 8100, there may be differences between the signal lines. The 8100 has three signal lines (two stereo and one for the microphone), whereas a regular set of headphones only has two signal lines.
In conclusion, this may take a bit of trial-and-error on your part to figure out the setup you want. No easy answers on this one yet. There are some solutions like the following, but it may not be what you're looking for: