linkf :
I cant afford buying another 7870 but buying a 7970 selling mine, and buying 1600mhz memory and a ssd, should i go for that? thank you for helping!
Or should i wait to have more money to do what you said?
Well, it depends. The 7870 is already fast enough to get good framerates on the majority of games at or near max settings, going bigger doesn't necessarily buy you a whole lot. It's possible that the SSD and memory will actually be a more meaningful upgrade than the video card.
So, without knowing what exactly you're looking for in your computer, I can give you my general guidelines.
First and foremost, a gaming computer needs a video card that meets your expectations. If you expect to play games on max settings with 60 FPS steady, then it's time for an upgrade. I'm a huge fan of the 7970, and it gets my wholehearted recommendation. A single one will max out most games easily, Crysis 3 being a notable exception (a single 7970 gets about 25 FPS on max at 1920x1080).
The SSD is a tricky thing to recommend for a gaming computer. As a rule of thumb, I don't recommend sacrificing the budget on components that will impact framerate, since that's really what the computer is all about. You should only pick one up if it's not going to mean you skimp on your video card, but if it comes down to the SSD vs. the memory, get the SSD.
The memory upgrade is going to be a nice, cost effective way to get a boost to everything on your system, including gaming. The gains going from 1066 to 1600 should be pretty significant, I'd expect noticeable improvements in framerates and system performance. You can get 12GB of 1600 for about $80 on Newegg. If it's in the budget, I think it's worth it.