Check out the ESI U24XL, a USB audio interface, for a great way to get quality sound between laptop and mixer or amplifier.
The ART DTI (Dual Transformer Isolator) will eliminate ground loops as a potential hum
source and provide an interface between RCA-, XLR- and TRS- terminated cables.
To add a couple of microphones, use a Focusrite Scarlett 4i4, a USB audio interface with quality soundcard.
