For me the best track to use hip hop vocals is Hydraulix 11, an absolute anthemn of a tune...but i agree some quality control is needed, most of the stuff i listen to and play (london based hard techno) seems to have that control...they've done it and moved on . I like good vocal samples in techno, if they add to the tune, RAW9 for example, but a poor tune is a poor tune even if it's got a quality sample.