I got my new PC a couple weeks ago so I thought I'd update this.
I did get the DGX and... Awesome!
I love this card and I found what I've been missing in PC sound all these years.
What I wanted was 5.1 through my Home Theatre and I didn't know if the DGX would provide that or not and that was my reason for starting this thread.
Once I had the DGX I used "pass thru" mode to pass a raw 5.1 signal from my PC to my amp via SPDIF optical and it works great. What has really impressed me is the quality of the audio though. It's not HiFidelity but it's light years ahead of what I had before.
So I've been very happy with my DGX... I still don't understand all the jargon (like what the heck "5.1 encoding" means) but I've managed to get a huge improvement in my audio quality and I'll take that.