I am an audio professional who has used every kind of audio interface and soundcard on the planet. However, I also have come to computers for audio-only applications very recently. I used to believe that a fancy sound card would take the burden off of my CPU. When I finally learned that this was not the case -- and that in fact, the drivers (ASIO) used to pipe audio out of the system would increase said burden, I decided to try flying without one.
The result is that I've been successfully using an integrated chipset to create some pretty good-sounding music. In my case, I rely on a very fast CPU to get me low-latency, so that I can use virtual synthesizer software to create techno/electronica music. My computer right now is an aging Intel Q8200 Dell desktop that I am currently upgrading.
It turns out that the latency won't be helped by using a better sound card, but I may go ahead and upgrade to one soon. The one thing that integrated audio can't do that well is to offer truly flat frequency response, and this is a bigger deal than a lot of people may realize. I should definitely be monitoring my mixes through a better card, because right now I have no idea what frequences are being boosted and / or cut.
So, in short -- if you just need to get the music happening, you can always use ASIO4ALL and get nice low-latency performance. In any event, you'll need a powerful CPU to deal with the latency, especially if you want to play synths in realtime. But if you want to get true frequency response, go with a good sound card or audio interface. Your ears will thank you for it.
