Thats not a really good question to ask me... I'm a sound engineer... my "computer" speakers (studio monitors) cost $1,000. So, its up to you
I dont know your budget/income, and what you can afford. If it were me, there would be no question. I would probably have that before I bought a 5.1 system. Digital outs are pure and raw information that your speakers will decode the way the sound engineer intended it to sound (As long as you disable EQ, CMSS, and all the other crap).