The coax digital out is the jack on the far left of the picture, above.
I picked up the Platinum version yesterday, and I must say it doesn't disappoint. Without all the bells and whistles, there is a noticeable improvement in mp3 and lossless playback from my vanilla Audigy 2. To my ears at least, I am hearing details which I previously heard only with headphones. That doesn't mean to say that speakers sound better than headphones, just that I appreciate the more detailed "resolution", for want of a better word.
My desktop speakers are Logitech Z680s. typically on Stereo 2X mode. Headphones are 50ohm HD595s.
I like the automatic speaker cut-off when you plug in headphones. That was always one of my gripes with the Audigy 2; I'd spend a few minutes reconfiguring volumes before I could settle down to listen to anything. The X-Fi has a separate headphone configuration and automatically applies that config when it detects headphones.
The remote control actually made me grin.
I don't know if it's terribly practical for my everyday use since the PC is beside my right knee, but functionally, I like it. The remote and OSD are nicely responsive.
I've read many people saying that CMSS-3D's effect on music is great. I heartily must disagree, but this is my opinion only. On headphones, I feel that the soundstage has been mushed, and the mids (I think) have been pushed up front. I need to do some more listening through the speakers to tell if they are similarly affected.
I haven't done enough critical listening with the Crystaliser to say whether I like it or not. Certainly, it makes things slightly louder, but the effect is different than if I had simply turned up the volume. Perhaps it just amplifies certain frequencies. All listening so far has been with 250+ bitrate mp3s and flacs through Winamp with the SSRC input plugin.
For music overall, a definite improvement over the older Audigy 2 card.
Gaming is clearly where this card excels. The placement and rendering of discrete sounds is top-notch. Call of Duty really came to life and I felt more immersed in the action. Half Life 2 had me reloading previous saves to play and "hear" it again. Audio in HL2 was already impressive; much more so now on the X-Fi. The biggest surprise however was on Guild Wars. I could hear my toon's footsteps clearly (I had never noticed before), and was surprised to find that the sound changed with different surfaces. Walking on sand, running over cobblestones, through grass, etc.
I imagine that CMSS-3D might work quite well with games, but I haven't tried yet. Certainly the test audio on the control panel conveyed the feeling that a helicopter was circling your head.
I do wish that more output options had been made available on the back of the card itself; I miss the firewire connection, and I still wonder why they didn't include an optical out. Granted, there's one on the I/O drive, but I feel that the breakout box is more for temporary connectivity, rather than long-term.
Add me to the growing ranks of those who've taken the plunge, and come up for air with a smile on their faces. I'm really enjoying this card.