leander1016 :
plz tell me which graphic or monitor or whatever would be the best
and would this pc play all games
That's why I asked what the system was for. I had suspicion.
The 5670 is a low end card. It is a bit better than the radeon 3870/ 4670. It can play most games at lowered settings. If you play at setting around 720p, you should be fine for most games.
I had a 3870 for quite a while. I don't mind lowering setting but I do mind lowering my resolution. I also really like to have 50+ FPS. I can compromise this in Crysis though. This is the reason why I could not play BFBC2 or Cryostasis. I recently upgraded to a 4850 (equal to a 5750/GTS250) and can now play some of these games more comfortably.
Your 20" monitor is likely 1080p or possibly 1200p. If you don't mind lowering the settings of more demanding games to 720p with reduced quality, you won't have much of an issue with the 5670 but I would expect to be upgrading for newer games in the next year or 2.
If you can afford it, I would recommend the current range of GTX460/6850/6870. Well worth their price. If not, the 5770 and 5750 and GTS450 are good cards, but not as worth their price if you can find an older 4850/4870 for sale. Usually they go much lower and except for the 5xxx supporting DX11 (not a big deal now. Even not having DX10 still isn't a huge issue) the 4850=5750 and 4870=5770.
If you cannot go any higher with your graphics card, and cannot find a used 4850 or similar from someone for a decent price (I got mine used for $20 off a guy!), then keep in mind what I said about settings and your gaming ability and don't expect anything higher for the price. But you still can play most games at lowered settings except perhaps Cryostasis or Crysis. If you do decide to get any video card higher than a 5750, I recommend getting 4GB of memory as opposed to 2GB. I had no issues with 2GB system memory with my old card because the settings required in some games to push past 2GB would have required a better video card but now with my 4850, I'm glad I have 4GB of system memory.
Other than that though, your system is a good budget system. Just one more suggestion: If you don't intend to play more CPU intensive games like Dragon age, BFBC2 or a few others, Consider getting an Athlon IIx2 and upgrading the video to a 5750 instead. It will keep the same price and be more capable, except in those more CPU intensive games.