Ok a quick backgrounder.

• ALSA can handle multiple devices
• Devices are assigned a "Slot"
• Slot - 0 is the primary, prefered, default device
• all the index = -2 stuff in modprobe.d/alsa-base.conf tells alsa not to let those cards have slot 0
• thus snd-usb-audo never gets slot 0, thus hard to find and use without something like the gnome-configuration panel.
• Commenting out the line that sets snd-usb-audio to index = -2 should let it grab slot 0
• thus primary, thus easy to use.
• If it is a mic only you'll have no audio out. but can at least see if the mic works.
• F6 in alsamixer (console) will let you select between cards. Not sure is just settng the input on a second card is enough to make it active.
• You can manually edit ALSA config files to set ALSA up so snd-hda-intel is for out and snd-usb-audio is for in.. that is beyond what I can explain here.