I have a system below:
Pentium D 2,8
2*1 Gb Kingston 667 mhz. Ram
AOpen 300w PSU
Asus p5 LD2 motherboard
160 gb Sata HDD
I've already using Geforce 6500 graphic card.
Which graphics card would u suggest with a budget of about 80-100 $
Well your PSU is a bit of a worry. Never heard of AOpen as a brand. Suggest changing that to something like Gigabyte Superb 460W or Corsair CX400.
About your card 9600GT is certainly a bit more powerful than 4670.
I have never heard of HD4730. When was this released?
Whatever you do change your PSU first. Otherwise i wont even do good with a HD4670 in it as well.
I have now learned to advise people to stay away from that PSU, coz i have replied to more than 100's of thread in my past 5 years of forum life, about people saying they have fried their PC's coz of this PSU. And the number is not a random number. It really is more than 100!