800 shaders in 40nm is a paltry improvement. RV800 shader per shader is slower than RV700. You need to get past the 800 shader core to 1440 or 1600.Looks like the 5750 might be a 5850M, which isn't so bad.
https://forums.macrumors.com/showthread.php?p=10671982&posted=1#post10671982
http://www.pcidatabase.com/search.php?device_search_str=hd
has a heart and will let me swap for the new one or just let it go? I have been contemplating all day whether or not it is worth the hassle....