Juube, The QS8 does not have a USB port. So the only way to connect to your PC for midi is using a midi interface. You have 2 choices.
1. USB midi interface (eg M-audio) - 1x1 would suffice. Connection will depend on what you want to do - whether you want to trigger softsynths/VSTis in your notebook, or for sequencing and eventually playback using your QS8 sound. If it's for triggering VSTis, connection will be:
QS8 midi out -> midi interface midi in -> notebook USB
If you want to sequence and playback with your QS8, you'll need the above connection PLUS:
Midi interface midi out -> QS8 midi in.
2. Audio interface with built-in midi - IF you are going to get an audio interface anyway. If you're using a notebook, firewire is the way to go. If desktop, then the choices would be firewire or PCI/PCIe. There are USB audio interfaces, but they are slower than firewire.