Fcpx and gtx 970 with 4kUHD files

Hi community, I use fcpx with 4k video. I just installed a gtx970 and the gain is minimum compared to the internal GPU. The R9 280x we tried to instal never worked (XFC brand) I'm a little disappointed. I would like to have fcpx work fluidly with a filter or two on in real time. Maybe I need another gtx970?

Thanks for your advices

PS: I have a ssd sytem and a raid 0 for files, I even tried a ssd for file, doesn't change anything