if you are only using premiere pro, a single gtx 1080 should be enough. if you are using other non-adobe software that uses mostly gpu power, then two gtx 1080 may be needed. it will depend on the non-adobe software you plan on using...
there are some problems with the new gtx 1000 series with adobe's software, but should hopefully be fixed soon with some new drivers from nvidia. GTX 1080
if you need a card right now, the new 1000 series may be sold out. the gtx 980 ti cards should be getting marked down and easier to find, but would be slightly slower than the gtx 1080 and wouldn't have the new 1000 series 10bit/HDR features. i haven't seen confirmation that these new features work in adobe software yet...
the radeon pro duo has two gpu chips on a single card, with only 4gb each to get 8gb total. it still functions as two cards, so any software that doesn't work well with two cards won't work well with this card. two nvidia gtx cards could have higher total memory, from 12-16gb+ between two gtx cards. two gtx 980ti or 1080 cards would also be faster.
the m5000 quadro is a very expensive slow gtx 980. most video software does not make use of the extra features in quadro cards, except the 10bit display output. a display out card from blackmagic or aja can get around this issue if needed, often for cheaper than the quadro. the gtx 1000 series is suppose to offer 10bit out as well, so if thats true, there will be no need for quadro at all with adobe software.
the amd firepro w8100 is amd's version of a workstation card. same situation as the nvidia quadro, expensive and not needed. however amd card's do not offer cuda (nvidia cuda), so if you have any software that needs cuda, amd cards won't be an option.
Hi has you thank you very much for your answer so the best would be a SLI 1080?
Did you forget to remember that SLI has been known to cause serious issues with the Adobe programs, especially ones that use the GPU to accelerate rendering? In addition, SLI does not double the available graphics RAM at all - but instead, uses half the total graphics RAM to mirror the other half. Thus, buying two 4GB cards and then SLI-ing them would still give you only 4GB - not 8GB - of total available graphics RAM.
Although Premiere CC supports multiple GPUs for GPU acceleration, it does not support SLI or Crossfire at all. Any multiple-GPU configuration with SLI or Crossfire enabled will be forced to run in software-only mode (GPU acceleration disabled) to avoid crashes.
ok thank you for your answer suddenly you you advise me as what graphics card?
what graphic cart do you advise me ?
Sorry, for my translation ....
one gtx 1080 is good for most computers with adobe software.
not enough information of your computer software usage to recommend two gtx 1080.