You know my views Trt, dont get too hung up on the shader thing as there are plenty of modern games that the 7900GTX beats the 1900XT at some games just prefer more pipelines, some more shader engines, its all down to the architecture of the game, take Fear for example.
To me as I said in our PM's in 3D Marks I think the 7900GTX would have the edge and is probably the faster card versus the IQ and HDR/AA running simultaneously, personally haveing both ATi (1800XT 740/900) and 7900GTO (a GTX @ 710+/840) I do not see a great IQ difference but the 1900XT has probably better IQ than the 1800, although the 1800 still beats the 1900 in some benches
Sell both the cards......I'll sell you a brand new 1800XT you pocket some cash
but I would never sell the GTO!!