Don't know where you live but cards are cheap in Canada.
This card is alot better the a DX1 and alot cheaper then most ASUS.
Considering it has the C-Media CMI8788 Oxygen HD PCI Audio Processor found on ASUS XONAR DX2.
AuzenTech X-MERIDIAN 7.1 2G
http://ncix.com/products/index.php?sku=57405&vpn=AZT%2DXMERIDIAN7%2E12G&manufacture=AuzenTech&promoid=1320
http://www.ncixus.com/products/index.php?sku=57405&vpn=AZT%2DXMERIDIAN7%2E12G&manufacture=AuzenTech&promoid=1320
I have X-540's which are quite good for the price but would have many flaws revealed by really good soundcards.
I think the DX1 and Meridian 2 are too good for those speakers though.
I think the Asus DG is a better match.
http://ncix.com/products/?sku=56330&vpn=XONAR%20DG&manufacture=ASUS
http://www.ncixus.com/products/56330/XONAR%20DG/ASUS/
I currently have an Audigy 2 ZS hooked up to the X-540's.
Have an older pc with Audigy 1 SE and X-530'S = garage system.
Auzentech Forte and old discontinued Yamaha 2.1's still haven't heard better pc speakers 40w sats/80w sub.
Auzentech X-Plosion C-Media CMI8770( same chip as OMEGA HT Striker) paid $35 for card and Logitech Z-5300.
If your're new to this the ASUS DG(has a headphone amp) and X-540's is a good place to start.