I honestly can't remember the last time I discovered a new unknown to me author at a large Chain Bookstore. Now if you want to buy one of James Patterson's 7 current releases sure ... he'll be right by the front door at eye level. Guaranteed. Right next to the calendars, Burt Bees lotions and stuffed bears.
I find new stuff to try at Amazon almost daily though.
Advances are a tricky subject. I'm not convinced the focus for an author should be on convincing a publisher to give you a book advance. I think that the days where a Publishing House will accept that the vast majority of their contracted releases will lose money are dwindling rapidly. Rather, how about nudging the publishers into finding a way to generate higher book sales? Would everybody along that supply line benefit from that?