I would think somewhere around this tier
Nvidia
Discrete: 8800 GTS 640 MB, 9600 GT, GT 240 (GDDR5)
Go (mobile): 9800M GTS, GTX 160M
Discrete: 8800 GS, 9600 GSO, GT 240 (DDR3)
Go (mobile): GTX 260M (96), GTS 150M, GTS 360M (DDR3)
AMD
Discrete: HD 3850 512 MB, HD 4670, HD 5570 (DDR3), HD 6570 (DDR3), HD 6670 (DDR3)
Discrete: HD 2900 XT, HD 3870, HD 5570 (GDDR5), HD 6570 (GDDR5)
Mobility: 6500M (GDDR5), 6600M/6700M (DDR3), 7730M
Mobility: HD 3870, HD 5730, HD 5650, 6500M (DDR3)