>Read about the stock image sites. They have a search function >that sorts out (eliminates) lower size images first. For that >application, FX is a must.
I think you may be misinterpreting their rules. To the stock guys, a 24MP image from a DX D3200 would be equal in "size" to a 24MP image from an FX D600 - there would be no reason to disqualify the D3200 image on that basis.