Hey, bh.
Let's work back from the PC.
Does your software support recording 8 channels at a time? Some of the cheaper entry level packages don't.
Does your soundcard support recording 8 channels at a time? Most don't. If you mix with a mixer, and record the stereo out, you will not be able to manipulate the different channels, like turning up the snare.
Do you have enough preamps?
Finally, do you really need to be able to record that many channels at a time? There are a lot of ways to work around that.
It might be better to be able to record 2 or 4 channels very well than 8 mediocrilly.