Hi Everybody! M new here n need some answer`s , actually m confused and need advise or suggestion too , my problem is graphic card i have HP DC 7600 system with 945 Board Intel inside Pentium D 3.4 Gh Pro , 2 Gb DDR2 Ram`s , 365 W PSU and Nvidia GeForce 9500 GT 512 Mb video graphic card , the problem is as i told my graphic card when m playing heavy game`s for example Alien`s vs Predator`s 2010 game is crashing and hanging and making me so nervous by the way i want to change my card to better one a few one i have in mind but i really don`t know which one is better ( like when i got it i don`t think to change it for year or two or it depend on my money condition so that`s why i want a good catch ) , they are ATI RADEON HD 4870 1Gb , Nvidia GeForce GTS 250 1 Gb and Nvidia Ge Force 8800 Ultra 768 mb if you ask me frankly i want to go for ATI RADEON HD 5770 1 Gb but i really wandering if i even can find it in used condition , to buy a new card right now the thing out of my pocket but those 3 card`s if i buy them second hand i can buy each of them approximately 115 $ in urgent , especially m interested in HD 4870 1 Gb very powerful card but what you guy`s suggest me . And there is another question if i buy one of those card`s changing my 365 W HP Branded PSU is really necessary ?! I appreciate any help and thanx in advance .