you can record 8 tracks at once, right, first record scratch track, one line for each piece (1 overhead track on the drums). Now you 've got the whole song that your can listen back to for reference, through any Headphone amp.
Now you do each track over, one at the time, while listening to the scratch tracks. Of course as you get a good take on each one, you dump the corresponding scratch track. Since you are recording on a computer, I strongly suggest the ART HPFX(build in vocal effects), the vocalist will thank you for it. Being a singer myself, I know how much hearing yourself dry, or trough plug in effects, can take away from the feeling of a song.
Have fun...
Drums will drive you nuts