Considering the size of the quilt, I would get the 1 inch. You can also find the ones with the decorative balls on the end. They look pretty nice. :)
Also remember that a lot of the ones you extend will want a brace in the middle as well as on the two ends. So, a thicker rod will be more likely to hold the weight without that center support, unless you do a tab top hanging set up like on curtains.
I can't wait to see this quilt you keep talking about!