I currently have Altec Lansing ADA890 Speakers, which are currently connected to my Dell XPS 430 via the analogue green cable. However, I would like to know if I can use a digital audio connection and if so , would this increase the quality of playback. I have Spif output on my sound card and subwoofer along with full 7.1 connections on the back of my pc, please let me know which cable to get?