#1
i am planning on recording my band through an M-audio soundcard.

i am thinking about recording the guitars and the bass using the "pre-amp" out and line out jacks. on the back of the amps.

when connecting from pre-amp out or line out to the line in of the sound card, should I use a speaker cable or instrument cable?
#2
go out of the line out. that will give you a line level signal which is what the interface will be looking for. for that, use a regular instrument cable.