*sigh*
TBH there arent any more "pixel" pipelines in current GPU architecture...I've tried to relate that. That being said, Nvidia doesnt have a 48 physical pipeline GPU, neither does ATI. The approach is in shaders where an ATI GPU can shade 48 pixels per clock and Nvidia has there "quad" assignment....so pipelines arent really anything that are considered existent even by the manufacterors.
So with that small rant aside. My personal choice for GPU (if you have the $) would be an X1900XT.