HD 4000 is MUCH better than a 6800U for anything using shader model 3.0 or higher.
actually it's probably better than anything older than a 8800 (late 2006) series.
a X1950XT will maybe get close to it (3dmark06 score is close), but because of how poor is the driver support and old architecture with with "vertex and pixel shader processors", I think the HD 4000 is always going to be better for DX9C games, and the HD4000 supports DX10/DX11, the X1950XT does not..
so I would place the HD 4000 higher than anything older than a 8800GTX.