Greetings, my wife and I bought our son an HP Pavilion P7-1500 PC for Christmas 2012. It came with a GT 620 graphics card, which isn't allowing him to game very well, even at 1600x900, on low requirement games like the new Sim City. He's new to PC gaming and is just starting to play Sim City and some games on Steam and wants a better card. He has met our grade requirements and we're now going to buy him one, but his PC only has a 300 watt power supply and I am concerned that the cards he wants, might not work.
He wanted a hd 7850 like I have in my PC, but I told him that is far beyond what his PSU can handle, so he is looking now at the hd 7750 or the gt 640. Here are the cards he is interested in:
I'm picturing this 7 year old kid trying to make the argument to his dad for a Radeon 7850. He brings up statistical data related to relative performance and also submits a price/performance ratio summary.
Joking aside, I looked up the respective TDPs of the GeForce GT 620 and the Radeon HD 7750 to see what kind of power requirement increase you would be looking at. Apparently, the GeForce GT 620 is just a rebranded Fermi GeForce GT 520. The TDP of that card is 30w. On the other hand, the Radeon HD 7750 is based on AMD's latest GCN architecture. It's very efficient compared to Nvidia's last gen cards. It's TDP is 55w.
If you were to install a Radeon 7750 in place of a GeForce GT 620, the power difference you would be looking at is 55w - 30w. I might be comparing apples to oranges here, but I think this at least gives some perspective as to how much additional power demand you'll be experiencing.
I hope I could help at least a little bit and best of luck to you.
Go for a 7750 it is a good card for medium gaming played far cry 3 bf3 mw3 and many games on medium high keep the resolution ft 1600x900
7750 is a very good for your kid and since he is new in the gaming he wouldnt have any problem with it ,300W PSU is enough for 7750 and no ddr3 please go for 1gb ddr5 it is very good card as i'm using it