Displaying posts in mixed format

I am playing with a design idea, whereby I want to have the most recent post displayed full width of the content box, with a decent sized snippet. Then I want to put the next posts in horizontal rows (three across, maybe two rows deep), with a small snippet. Then on subsequent “next page”s to have only the three across small snippet format.

The three across part doesn’t seem to difficult, using divs that are floated left, one third the width, inside a container to limit them to three across.

Its the counting that has got me scratching my head. I would have to assign one div wrapper and snippet size to the fit post, then a different wrapper and snippet size to the remaining. Plus then the post per page would also be different between the default page (7 posts total) and the subsequent “next pages” either 9 or 12 posts (whichever works better visually).

Is there a relatively straight forward and simple way to do this or do I need to get a case of red bull and resign myself to the computer desk?