I just bought a laptop (Lenovo y500 with 8gb RAM, i7 and nvidia geforce 750m) and am looking to add to the graphics by purchasing an sli graphics card to replace the ultrabay. I cannot find a 750m sli card, so would a 650m work in tandem?
The 650m will not work. The 750m ultrabay card is in small supply with a pretty high demand. It will pop up in the lenovo store every so often. You could try to contact lenovo for more info. You will probably also need a new power brick. You can check the sticker on yours, it is probably the 65w version. You'll need the 170w version.