help with gfx cardi've got an amd firepro v490

i’ve got an amd firepro v4900 http://www.newegg.com/Product/Product.aspx?Item=N82E16814195109
and an nvidia gt 640. http://www.newegg.com/Product/Product.aspx?Item=N82E16814500256

what i’m wondering is which of these is going to give me better viewport performance. i’m using ubuntu and i’d probably just stick with my firepro if i didn’t end up jumping through hoops to install the amd drivers each time i try to update them.

i’m less interested in cycles gpu performance here unless it’s as a secondary card to only drive a preview viewport window. i originally bought the 640 as a cheap card to try that out but ended up not using it that much for the purpose. i installed it in a separate machine because i have no idea how to get that going with an AMD card as the main card in the box. any help you could point me to there would be great as well.

Theoretically Firepro v4900 should have better viewort performance as thats what Firepro and Quadro series are meant for. Its useless for Cycles though as AMD haven`t fixed their OpenCL support.

thanks. =)