472kHz WSPR - RX only now with preamp

Since 2055z I am on 472kHz RX only with the preamp in circuit. I shall stay on overnight to see if any new stations are copied. Up to now the conclusion is the preamp improves the sensitivity and S/N of stations, but I have copied the same stations without the preamp. What I need are a few new (to me) stations right on the threshold of copy.