Difference between audigy 4 and onboard ac-97?

[Energize]

Just bought one of these, never had a seperate soundcard before, but I thought I should give it a go, how much difference will there be between this card and the ac-97 I was using before?

Also can someone reccomend me some headphones to take advantage of this card?

 

[BoomAM]

I'd say a big improvement.
I know that the difference between my onboard AudioMax 7.1 & my Audigy1 was quite a lot. The Audigy was clearer and 'warmer' sounding.
So going from a normal AC'97 to a Audigy4 should be like night & day.