Hi Rob,
This is hard to say, and obviously you expected it to be better instead of worse.
Besides the below, let's keep in mind that nobody that I know of (for XXHighEnd) uses a PCI Express soundcard. And, while I myself would expect that PCIe should be better than normal PCI, it is very different anyway.
First, however, I'd look into those "DSP" settings in there. The "normalized volume" could be a first you overlooked, or even set on purpose.
I think you will know that all of these things should be shut off, right ?
Now, since you will be using this for analogue out (opposed to SPDIF Passthrough), anything could differ, because you're just using another DAC. And you won't hear me say that Realtek is specifically bad (in fact it seems to be the only mobo chipset people use here and there). So, I'd say that when nothing else can be found (the DSP stuff) it may very well be the DAC you are hearing.
Lastly there's this :
Customize your sound color effortlessly via swappable OPAmp socket
This looks like a virtue, but may also tell you that an opamp is in order while in the Realtek there is not (this needs diving into that chip), and which - when one has not and the other has one - is a good reason for very different sound.
I hope this brings you somewhere ...
Peter
