I have used Steinberg product for some time but since I have Avid MC for my video editing, I want to find out more about Pro Tools since I read that Pro Tools is more compatible with MC than Steinberg Nuendo. I have used external hardware that connects to my internal audio card. No, I have never used an external hardware that uses USB or firewire before. Make sure you take a look at THE SOFTWARE COMPARISON before you dive in. You may also see discussions about bit depths and sample rates for each DAC. Most options for PC do have an amplifier, but you will find high-end audio DACs that require a separate amplifier. If so, Pro Tools 9 might not be for you unless you want to buy the rather expensive Complete Production Toolkit 2. First, your external DAC should have a built-in amplifier to make it more economical and to take up less space. Maybe something like this Sound Devices unit? If you are on Windows, you need to make sure whatever you decide on has compatible ASIO drivers. Most of the rack hardware you see is either USB or FireWire and does not require a separate sound card.