Triple screen user new GPU

I am a triple screen screen user looking to fix slow texture loads on FSX mountains and detailed scenery when using ORBX. I am using a single GTX 770 (2GB), so would like to know whether purchasing a new GPU like a 970 (4GB) would fix or greatly improve the.issue on my triple screen set-up. I have already tweaked the CFG with increased LOD and some other suggestions from users, but think I have probably pushed about as far as I can go with the 770. I am also using an i7 4770K CPU but cannot overlock on my Intel H87 board, so would the GPU upgrade be a worthwhile investment or should I save the money for a new PC? I'd be grateful for any advice!