we have chosen to buy a quad sdi magewell .
this brand is widely loved on this forum .
we 'll keep on using , to , our PCIE xcapture , (as only the USB3 one causes those problems) .
we bought it 2 years ago , we already have it .
as we'll probably be on windows 10 , we won't use my USB3 x-capture .
drivers had been updated for win 7 and 8 , not yet for win 10 .
i'll use it , on another computer win7 based (had no problems with it last month , when last used it) .
trial and error , that's exactly what we just did today .
adding a graphic card , in order to get it as an " external " available set of 2outputs ,
should achieve what we're needing .
to get SDI out , if needed , we'll simply use a converter .
our budget is correct , but doesn't allow us everything .
so, this final info , regarding the second gpu ,
surely will lead us to go with a quad sdi magewell capture , probably the gigabyte GTX 980 ti , and some (i don't know yet which) Nvidia dual outputs second GPU .
if ever , we face other problems with our PCIE X-capture , we'll probably go for another magewell , single channel .
Things now appear much clearer to me ,
thanks to your helpfull answers .
It is much appreciated ,
and i apologize , all this may start to be a little confusing .
as a PC beginner , i miss some obvious knowledges , they are the reason for this thread .
to me , it is quite less confusing now ,
thanks to you all ,
Matthieu