12-24 on the D700 works but at just under half the mp because it would be in DX format. Probably just over 5mp. So with your 12-24 on a D700 you get same fov as with your D80 but with half the mp of your D80. Not really worth the D700 body upgrade if you do not upgrade to FX lenses. To really get your moneys worth out of buying a D700 would mean upgrading to any non DX wide lens. Example 14-24 f/2.8 @ $1799.00 D300 with your 12-24 is perfect,unless you have the $4800.00 to spend.