If you are listening to music from your computer through the Crack amp, then you already have a DAC (somewhere). If you are using a sound card on your computer then the DAC is embedded on that card. DACs are everywhere in this day and age. Every digital music music player has one built in, every cell phone, just about any signal processing gear for music or instruments will have a DAC if it is digitally based.
That being said, not all DACs are created equal. Some will only convert the basic digital files like the MP3 and MP4/AAC with 16-bit quantization. These are what you find in portable music players like the ipods and others and here the term "DAC" would be used to refer to the specific microchip used to perform the actual conversion. Other DACs can handle some amazingly high-resolution files like the 24/96 (and higher) digital files sold at HDtracks and other places. They also have much more sophisticated analog circuitry and come at a much higher price. Many of these "DACs" are usually stand-alone units with no storage, just digital-to-analog conversion. Others provide interface software to control your computer library (like the Logitech series) and still others offer storage space for your music files (think super-fancy desktop-sized mp3 player). Here the term "DAC" is used more generically for the whole device.
In a quality audio system, the DAC can make quite a difference indeed. It will be well worth your time to do lots of research first. Become and expert, then make an informed decision based on your needs, budget, etc.
