X-Fi HD USB or Xonar DG?

The X-Fi HD USB lacks the EMU20k1 or EMU20k2 that makes an internal X-Fi card a true X-Fi, and that DSP is needed for all the gaming features. If anything, given the way it's advertised, Creative's targeting music-loving audiophiles with that product.

If you want to keep your Z-5500s connected, I'd suggest going the Xonar DG route since it supports Dolby Digital Live for certain, and feed those speakers that way. Normally, I'd suggest just leaving everything connected via analog (the Z-5500's DAC isn't exactly top-of-the-line), but there aren't enough jacks on the DG, and front-panel audio headers generally introduce a lot of undesirable noise.

However, I don't know if that'll introduce any software complications. I don't have a Xonar DG (Auzentech X-Fi user here), and I don't have any surround speakers to send AC-3/Dolby Digital over to while still leaving my headphones connected. I don't think there should be any issue besides switching default devices in Windows, though. (Analog and S/PDIF-out are separate in the playback devices section.)

You could get a splitter, but that still doesn't get around how the sound card's control panel is usually set to either speakers or headphones. You might have to switch between them to get the ideal sound. (For instance, let's say you want to watch a movie at night, when using speakers would be undesirable for anyone else in the house. You'll probably have to set it to headphone mode to get the Dolby Headphone option if you really like the surround effects.)

EDIT: Oh wait, I forgot. Movies already have their soundtracks in Dolby Digital and/or DTS to begin with, no need to encode on-the-fly; just bitstream that over to the Z-5500's decoder. That makes the X-Fi HD USB a very compelling option indeed if feeding the Z-5500 digitally, if a bit more expensive. The external USB approach might just come in handy later on...

I only have experience with the X-FI HD. It's like a Swiss Army Knife. With USB to S/PDIF, S/PDIF to USB, ADC, and DAC functions, plus,  pass through of 24/96 to digital inputs that can handle it, the X-FI is as versatile as it gets. I use all of it's features for playback and recording of computer audio to/from my HT. As far as its sound goes, it seems to be as transparent as it is noiseless. I am satisfied with mine. With it, I have digitized my vinyl into my iTunes library and have integrated the computer as a source component connected  to  my HT, what more is there?

Quote:

Originally Posted by sterling1 

I only have experience with the X-FI HD. It's like a Swiss Army Knife. With USB to S/PDIF, S/PDIF to USB, ADC, and DAC functions, plus,  pass through of 24/96 to digital inputs that can handle it, the X-FI is as versatile as it gets. I use all of it's features for playback and recording of computer audio to/from my HT. As far as its sound goes, it seems to be as transparent as it is noiseless. I am satisfied with mine. With it, I have digitized my vinyl into my iTunes library and have integrated the computer as a source component connected  to  my HT, what more is there?

Totally agree with you, The X-FI HD is a good product, not expensive and versatile. I use it with my ATH-M50's and I'm pretty happy whith it. I used it asio4all, all you have to do is change output to wave/midi in asio4all device controls manually. I bought it because I'm kinda of a gamer too. Haven tried the EAX feature but its there. Currently using the DSP of my media player. 

As for the OP, you have to feed your speakers via optic out, of course there is no cons in doing so, I usually feed ac3 signal to my HTS with no problems. As NamelessPFG says though, you would be using your speaker systems DAC, which is the only possible downside of the setup but it will still be better than the realtek onboard sound. Your M50s would go into the Headphone jack via 6.3" stereo plug. Simply switch outputs via playback devices (right click sound icon -> playback devices) to switch from speaker to headphone output. And no you can't have both outputs at the same time.

Lastly, though the X-fi HD has some sort of gaming related features like EAX and surround sound headphones, it is more targetted at music lovers. For a usb setup it has a pretty nice SNR at 114db. Oh and I disabled all the enhancements since they are useless :3