After a lot of thought, I went a completely different route. I ended up buying a Topping TP30. It's a small, but high quality t-class amplifier with a built-in USB sound card. I'm running this into a small pair of bookshelf speakers, though it does also have a headphone jack on the front.
The pros of a setup like this is that you avoid pretty much any interference due to the sound card being in the amp, and not the PC. You also get something that can actually drive speakers, unlike most PC sound cards.
The cons are that there is probably a bit more lag, being a USB sound device. It's a purely stereo setup, so no fancy dsp or surround features. There is also no mic input. I have a seperate pair of USB surround headphones that I use for games, and my webcam also has a mic on it, so this wasn't an issue for me.
The cons are that there is probably a bit more lag, being a USB sound device.
Nope, not really. USB does not introduce any relevant latencies. I've seen home studios with USB sound cards that come with ASIO drivers. They can get 4ms latency out of them, which is pretty much the same they get with PCI cards. 4ms is waaaay lower than what ALSA uses to begin with (ALSA has about 20ms latency by default.)
It was first PCI-E Card I could find on market(A few years back i had only 1 pci slot taken for wireless card on Asus MoBo). It does require floppy power connection.(it will work without it, but will sound much more quiet, however i don't know if it wont perm damage card itself) But there are IDE to floppy connectors for power, so it's not problem. And I also have one of those attached to power supply.
It has mature drivers built into Linux kernel, so its compatible with pretty much any sane distro. Drivers were mature since moment I bought it and thats a few years ago.
it has 1x PCI-e, which means its fully compatible with PCI-E 16X. Don't worry about size difference. It fits just fine.
It doesn't have all bells and whistles that Creative can possible have, but problem is, all those bells and whistles are not available in Linux anyway.
I am not audiophile, so didn't test it with Jack, but I don't think you will hear anything that I didn't hear. After all I am only perfect and you are only human :P And funnily enough, good set of cheap ear plugs(Panasonic or something? Not Sony for sure!) can provide very nice sound with it. Deep Bass. No sound delays were noticed. I have tested over several thousands of hours with Heroes Of Newerth. APPROVED! :P
All 5.1 channels work. Were checked with Creative Speakers(crap, doesn't ever buy any wireless products from them, bought device, it failed in 2 months. Replacement didn't live for month, at that time I gave up. 700 euros down the toilet, will avoid creativein the future)
I run a ASUS Xonar DG which is a cheapo PCI-card with good quality (http://techreport.com/articles.x/19997). It uses a CMI8788 Oxygen HD Audio chip which is flawlessly supported in the kernel for some time. I think I had 2.6.38 running at the time I bought the card... Also pulseaudio works nicely with this card.
What it lacks is 5.1/7.1 audio decoding done on the card. But if you connect it via optical SP/DIF to an AV-Reciever (which does the decoding) that doesn't matter. It uses only little power and does not require an additional connector like the ASUS Xonar DX 7.1. But if you have no AV-Reciever and require 5.1/7.1 the Xonar DX is sure the way to go, like dimko said!