One weekend in Chicago, fine dining lunch, any suggestions?

[ltownhound]

I will be in Chicago this weekend for a bachelor party and have already posted about cheap eats around Wrigley. I would love to go to Alinea, Moto, etc. but I just don't have the time/reservations for a dinner at these places. Where can I go for an unbelievable fine dining lunch on Friday or Saturday? I would have to be able to walk in or get a reservation as of Tuesday. No real price constraints, within reason, but I would like to be able to get there and back from Wrigleyville in 3-4 hrs. This might be a ridiculous request, but any suggestions would be awesome. BTW I will gladly reciprocate for Boston/New England visitors who need advice. Thanks in advance.