Most of your rendering probably doesn't use the GPU that much.
Check with this page :
Photoshop graphics processor (GPU) card FAQ
....straight from the horses mouth...
That said, I PS does support OpenCL for some functions (odd, I always thought it was CUDA) so AMD will fare better than nVidia in that regard.
1) RAM and lots of it. 8GB is not enough
2) Get a fast, local SSD. Configure PS to use a 2nd physical drive for the swap, not the primary.
3) Faster CPU
4) Decent external graphics card
I used to work for the subsidiary of a very large camera company (no, sorry, was not Pentax). I dealt with massive graphics files, far beyond what normal users would have. No problem running with old Core 2 Duo machine even, but the IT crew stuffed my workstation with 32GB RAM and the 2nd drive that was exclusively used for PS swap space. This was not even an SSD
Please keep in mind what GPU are normally designed to do, they were often focused on 3D rendering. "Rendering" , stitching panoramic images is not the same thing.They can be used as specialized processing units now but that depends on the software supporting it (e.g. CUDA or OpenCL). The top-of-the-line Intel graphics is getting decent now but it isn't the one in your i5.
Also, if you're serious, go desktop. I use a high-end HP workstation laptop these days and it might be comparable to the ancient Dell desktop workstation I used to use. Your little consumer grade laptop isn't going to cut it. Sure, the paper specs look the same but when you dig down deep, there's a reason it costs less ... little things here and there, from RAM to HDD speed, etc. plus I believe it will throttle when your CPU starts heating up.