Nvidia kepler series gpu (670mx, 675mx, 680m) cards will not work in MSI sandybridge generation notebooks. It has something to do with the vbios. If you install those cards, you will get a no display output. It is because the card thinks the laptop has igpu support and expects that to be doing all the video work from boot. But since the motherboard doesn't support igpu (optimus), it can't utilize the sandybridge gfx core anyways.
The 670m is same as the 580m. It is one of the highest TDP cards, and will generate alot of heat. At a price point of $300 or more, it is not a viable solution. You will also need a heatsink, as the 560m one is not compatible.
I upgraded my 1761 (780dx barebone) to a 7970m card made by clevo. The stock vbios it comes with is for systems with igpu, so it cannot display to screen or hdmi/vga out. But there are dell/clevo vbios that can be flashed to the card to make it work on a system without igpu. I had to use a drill to shave off parts of the 570m heatsink to make it fit onto the 7970m, and had to use alot of thermal pads to fill in gaps between components on the card.
I did this upgrade because the original 570m gpu died and the system was out of warranty. Instead of buying a replacement gpu, I rather spend a few hundred dollars more to double the performance I had before.
There are still some annoying things like the motherboard EC cannot read AMD gpu temperature, so the fan doesn't respond if the gpu gets hot , but the cpu is not hot. So I have to use turbo fan button every time I play an intensive game.
Its best you do alot of research if you try to upgrade your gpu. Best place is to look at the MSI forum at notebook review website. Lots of material and knowledge base there.
The card was $435 + state tax / shipping for brand new. But getting the correct heatsink will be another $100. The GX60 heatsink will work without any modification with the 7970m. With a little ingenuity, I think the 560m heatsink can be adapted to work with the 7970m, just need some planning out, power tools, and thermal pads of various thicknesses.