Just to get Valenter back on original topic. For starting out you most likely won't need to record more than 1 or 2 tracks at one time. And, I don't know of any entry level audio recording interface that won't do that. If you get one that also performs midi in and out you'd be set for quite a while. The USB mixers that I know of don't have midi in/out. I'm getting good recordings and flexibility with playback and monitoring with a Behringer UMC204HD. It's audio/monitor outputs are connected to my Yamaha 12 channel mixer but the mixer is there to serve multiple purposes for me.

As you progress you may need to record a live drum set which usually takes at least 5 mics and 5 channels to 5 separate tracks. That would require a much more expensive interface like the Pipeline and Charlie are talking about.

I was just thinking that since you already have a soundcard, the Xonar, which probably has great ad/da converters and other options, that you could connect a mixer with phantom power and decent monitor routing to it.

But, ideally I think you'd be better off with a decent audio recording interface.

Does the noise in your head bother me ?