beeeno :
Asus has good cards, but I wanted some of the features that are still present in X-fi(OpenAL in hardware CMSS-3D) with the right audio plugins on software.[/quote]
ASUS supports hardware OpenAL 2.0. They also offer the same benefit as CMSS-3D via Dolby Pro Logic IIz and Dolby Headphone.
With a non hardware accelerated plugin, most of this is now done in software and does not sound that good to be honest(too much center channel for music, kind of ruins the stereo image when the singer has parts of their voice moving from center it sides when it is not recorded that way. Happens because certain frequencies get into the center channel more often then needed.). Ideally, I want NO center used with music, but do not mind the rear speakers being just a copy of the fronts(for 2 channel sources).
The primary driver of audio quality remains the DAC on the soundcard, the specific OAMPS used, followed by the driver layer.
While I would agree that the DAC plays the biggest role(in overall quality). The software upmix is very "bad"(software based X-fi cards). I found Dolby did not sound that good to my ears(again personal opinion).
As for the opamps, unless you are running a very good home stereo(and those now are all digital bypassing the sound cards opamps), most consumer level audio still uses 4558 variation opamps(X-fi is no exception to that rule). So even if you have the best thing you can get on the card, it will get limited when it hits the stereo/speakers. Just like all hardware, you will get a bottleneck somewhere.
Good to know that Asus has hardware OpenAL. Basic stereo mirror upmixing is easy to do on a hardware level, just not nice and automatic.
Are you running an Asus card by any chance?
I'd even go as far as to tell the OP that they may as well try the onboard to see how they like it first.