Well, ive been through this on here before.
I cant seem to record anything onto my laptop without it sounding like shit. I go from the booth output on the mixer to the only input on my laptop, and it sounds tinny and has a nasty background hiss.
The only solution anyone has come up with is an external soundcard.
Well no, your right - the inbuilt soundcard on computers is shit.
You either record it into the comp. quiet, and have high noise floor (that hiss) or record it hot, and get to hear what crap conversion sounds like clipping.
So, yeah, your right - you simply need a higher quality soundcard for it, which is going to mean an external one.
Is it just for recording DJ mixes, or are you looking to do some production on it? Additionally, do you think you might get into a Timecode based digital system at some point, because some of those systems come with a soundcard that will do the job as well...