buying a video card for computer vision processing

Hello folks.

I have a low budget right now and im willing to buy an used QUADRO P400 (2GB, 256core) for R$ 650 (brazillian real) or a unused GTX 1050TI (4GB, 768cores) for R$ 1700.

Both have a 6.1 compute capability according to cuda sheet (CUDA GPUs | NVIDIA Developer), so i dont know if the GTX is worth of buying.

My project involve real time processing of 4 cameras: 2 small blobs identifications in two cameras (1 blob in each camera) and pose estimation in the two other cameras (2x1, stereo).

So far, i can compute the blobs in real time (30fps) while the camera pose i have not calculated yet. Further, i have not used the gpu processing in my algorithm (matlab doesnt recognize my nvidia 6870) and I don't know much about it, and if it will really improve my processing. Moreover, i should worry about compute capability or RAM/cores of the video card to improve my routine?

Anyone can help me indicating what would be the best video card to my needs? Or tell me if the camera pose estimation can be easily processed in real time (30fps) with no gpu processing? i need 6dof of camera pose at 30fps