I have been lurking in this section for a while and read through the ample threads answered by audiophiles. In every thread I see Asus Xonar ST/X as the best recommendation for audio listening. Furthermore, Creative products are bashed down and sent to the back of the bus due to the so called low audio quality.
So, I pulled the trigger and got myself an Asus Xonar STX. After I had problems due to its length and was forced to re-arrange my whole computer inside, I managed to install it. I won't get into the the hoops I had with installing the ASUS driver because it is pointless. I thought Creative was crap but ASUS is not far.
I am running FOOBAR now via WASAPI and listening to HQ flacs, AC3s, DTS songs and ... what a sad audio card.Sound is flat with a lot of mids and while the distortion is close to non-existent, I cannot say I am satisfied. I spent 160 euros on a soundcard that is mediocre. Lack of treble and bass control is shocking! You can pump the EQ all the way up and play with the crossover frequency, the results are still not what they should be. The dynamic effect you get from a treble and bass knob and frequency separation is not there.
Many here on the headfi board need to have their ears checked because the recommendations they give are misleading. I've seen this 'you can train your ear attitude' which is totally false. You either have it or you don't and the majority does not.
In my family we are rather close to music and high quality (from opera singers, guitarists, to sound engineers). I grew up with them and with proper music and I inherited the capability of detecting good music from bad. Because I was out of the audiophile scene for a while, I opted to get advice from people who were up to date. How wrong I was.
The STX is awesome on paper and the frequency tests are close to perfect. It has its own opamp and this is its main selling point. My Creatve Platinum EX did not have all these fancy things and even my Auzentech and Titanium are of a lower quality if we look at spec wise.
Does the STX impressive spec sheet translate into real life? No it does not because the sound in my Klipsch and Senns is not as vibrant as in the Platinum EX, Auzentech or even the piece of poo Titanium HD.
A huge pro for the XONAR is the low level of distortion. Compared to the other sound cards I have the XONAR tramples them BUT the XONAR is FLAT! My Senns HD650 sound FLAT now 
A piece of advice, if you don't know what you are talking about, do not advise people. If you see a recommendation someplace from someone, do not act like you are an expert and recommend it too.
