The Asus cards have very sub-par quality.... especially at the $130 price point.
@Daft
To get the full effect, yes you do need a HQ sound card as well as some type of amp. But trust me when I say this... it is not a must. They will still sound infinitely better than what you are listening to know. Better hardware will come in time. Think of this as an initial investment. Over time, once you get some spare cash you can invest in additional equipment(sound card, amp, new cables, etc.) but for now the most sound(pun NOT intended) investment you can make is in the cans. 280's are an excellent set that have great potential, but they will still sound great on anything.
When I first got my 650's I plugged them straight into my NF4 onboard sound processor. They sounded amazing. When I got my X-fi Elite Pro, I was floored. Once I get the money for a good headphone amp and the skill with a soldering iron to mod my card, I expect to be floored yet again. Senns have the potential to be the greatest sound you will ever hear, yet at the same time, offer a performance that scales well on just about any audio equipment.
Also, don't buy into multi-channel or sound reflecting headphones. The former are completely unnecessary and the later destroy the sound. IMO, a set of headphones is not a video card and should be for more than just gaming. There is no point in dropping triple digit sums of money for something that only plays game audio well.
Oh, and just from a pure sound quality standpoint, this is probably the best SC for the money:
http://www.newegg.com/Product/Product.aspx?Item=N82E16829156005
I might expensive, but an excellent sound card that has been designed from the ground up for sound quality. Please note that it offer very little performance gain as compared to the X-fi series.