Upgrading sound card -- need advice

[OutpostCommand]

G'day,
since im getting myself some new headphones, I have decided it is time to upgrade my soundcard too.

Currently, I have an Xtreme Audio. Its not bad in that it does the job, but im looking for something with a little more 'oomph'.

I have had my eyes on the Asus Xonar cards, but I have two questions--

a) Are the Xonar cards the series which I should opt for, or is there something better ? (as in, performs better for a similar price)

b)If the answer to 'a' was that I should go with a Xonar, then I need a little advice --
quite simply, which one should I opt for ?
There seem to be a variety of cards:

There is the DX 7.1, D2 7.1, D2X 7.1...
I simply dont know which one to opt for.

Could anyone lend me a little advice on which one I should go for ?
Price is generally irrelevant as long as its under £100.

Some details which may be useful:
-My mainboard: P5N-E
-I have one free x8 PCI-E slot

Thanks in advance

 

[OutpostCommand]

Oh, actually one more question -- since im opting for high quality headphones instead of a speaker set, will the sound difference be all that much better than my Xtreme Audio ?

 

[OutpostCommand]

Aha, cheers. Ill look into their products.

Im planning to go ahead with the ATH 700s.
They sound like a great deal.

I havent got them yet though.

And im not quite sure what is meant by the term 'driving'. Apologies if its something really simple.

 

[OutpostCommand]

First and second time I read this thread, I still couldnt make head or tail of what was going on -- but third time lucky
I understand.

Ive done a bit of research too, and it seems the Xonar DX is the way to go.
Its cheaper than all of its Asus rivals (D2X, D2), but performs on a similar level.