To go on Neal's idea...i am not a big fan of the powder room on the staircase. I would simply combine it with the laundry area and relocate the entrance to the garage. use the same layout as the powder room has now, and put it next to the window. Do you really need the laundry tub? what is your thoughts on a stacking washer/dryer? You should have plenty of space there to make it all fit.
As for the dining and living room, I like the breakup between them. But if you have a great room, and optional media room, is there a need for a dining room, AND living room? Is the plan for them to be more formal? i think the great room is where you and your family will spend the most time. You might consider moving that break between living and dining to enlarge the dining room. maybe close it off completely and make the living room area smaller, and make it a den or home office? Maybe make the dining room at the front of the house, make it a little larger, and put the powder room behind that so its not on the stairs, an then you can leave the laundry room and garage alone.
Best of luck!