Help with upgrading my PC

I have 350€ or more if it makes a difference (roughly 450$). I would like to buy new graphics card (nvidia preferably) and memory, but as I am an amateur in this area, I want to ask for your help.

For memory, I cant decide if I want performance boost (SSD minimum of 120gb) or more space (HDD), but I do want it to be the lowest price possible as I want as much of that money to go to graphics card. Or maybe something else needs upgrading? I dont know but I would apreciate any advice.

My current setup:

  • CPU: Intel i7 920 (2.67GHz 4 cores)
  • VGA: nvidia GTX 275
  • RAM: 6gb of DDR3 (dont know the frequency)
  • HDD: SATA 2 - 3Gb/s 512GB of memory
  • MB: Asus P6T
  • PSU: Corsair HX520W modular power supply

Also, in relation to this. What happens if I have two different graphics card plugged in but obviously not connected with SLI? How does that work? Can I have my secondary display plugged into my secondary GPU so it will take the load of that display from main GPU? And could my PSU handle two GPUs?

I have honestly no idea about these things so thanks in advance.

 

Get a 670 or something and a 120GB ssd

What do you use it for?

Just gaming... and although my current GPU is not completely bad, it doesnt have DX11 and some of the games coming out have DX11 in minimal requirements... and that was final nail in the coffin :/

By the way, I thought GTX 670 requires PCI Express 3.0 x16 and my motherboard supports only PCIe 2.0 x16,
I suppose it wouldnt work if I plugged it in?
Same applies to SSD, they all need SATA II or SATA III but in my MB specs i can only find SATA, which is weird because my current HDD is SATA II at least thats what it says, Im really lost here... any help?

Im either missing something or Im going to need a new motherboard as well... :/ 

So, on another forum (because people here are not replying that.... often) I have found out that you actualy can plug PCI 3.0 to PCI 2.0 and SATA III to SATA (although Im still not sure about that because some people said otherwise).

I think I will go with AMD Radeon Sapphire HD 7970 OC boost (I wanted nvidia but I can get really good deal) and for SSD 128GB SanDisk Standard SATA III

But I dont know what kind of drawbacks are there in PCI 3.0 in PCI 2.0 and SATA III in SATA. I mean, can I get at least 80-90% of power from that graphics card? Or will that SSD even be faster than my current HDD in that setup?