At the very least you could use your 4-track as a mic preamp and get the same dignal onto hard disk that you can to tape.the reason i want to use my four track is i am not sure how to record vocals using my pc.
Depends on what you mean by "lots." 16-bit/44.1kHz digital audio is approx. 5 MB per minute per track. These days you can get 30 GB hard drives for around $100.also don't you need lots of disk space?
and what about quality