We're fast, but not always that fast at replying 
If you go with Steam OS, get an Nvidia card since it has the best drivers. If you want AMD, stick to Windows as it performs better with D3D. But overall Windows will probably play better due to the best drivers for both cards.
I'm not very well versed with AMD, but on the Nvidia side the GTX 750 Ti can handle 3-4x IR, depending on the game (above 3x IR is 1080 and above. Go higher than your TV resolution gives down sampling and a better picture).
You're going to want to overclock that G3258 to about 4.4-.6 for the best results in Dolphin and other things, which can be reached with the stock cooler.
If you go with Steam OS, get an Nvidia card since it has the best drivers. If you want AMD, stick to Windows as it performs better with D3D. But overall Windows will probably play better due to the best drivers for both cards.
I'm not very well versed with AMD, but on the Nvidia side the GTX 750 Ti can handle 3-4x IR, depending on the game (above 3x IR is 1080 and above. Go higher than your TV resolution gives down sampling and a better picture).
You're going to want to overclock that G3258 to about 4.4-.6 for the best results in Dolphin and other things, which can be reached with the stock cooler.