I'm a bit late with this. Online sales are a great concept but so far the takeup with wine is pretty low. The real issue is that larger wineries with larger advertising budgets naturally have greater exposure and make more sales. To give all a more even chance you could feature a small number of wineries each week (you have enough hits to make that viable) so that all have some chance of standing out in the crowd. Online shops are expensive but if it is successful (ie lots of buyers) then you will be successful by levying a small commission on each sale. Good luck with the venture.