Can I use my computer speakers and the HD6's at the same time?

Possibly, it depends on the computer's operating system, sound capabilities and connection type. If your computer is capable of doing so, our speakers will not prevent this type of use in any way.

For example, if you have a Mac running Snow Leopard or later, you can create a multiple output device to accomplish this. See the link below for how-to instructions on Apple’s site:

Creating a Multi-Output Device