What sound cards are availble for Mac>>>And is there any advantage installing a better one over the ones that come one the DP G4s? Maybe better sound etc etc.
I have the M-Audio Delta 4 and it works great. It's a PCI card with 4 1/4" ins and 4 1/4" outs, they have had Mac OS X drivers for over a year and a half, and they're very stable.
There might be an advantage in getting a USB or Firewire mixer instead, since they don't use up a slot, and some of them are quite powerful.