I have the emachines et1331g-03w and have used both a gts 450 and currently gtx 550 ti with the stock power supply. on the side it says fsp group, 300 watt 80 plus. i am hooking them up with 2 molex to 6 pin connector and they both will run just fine. both of these cards are recomended to use a 400 watt psu, so maybe i got a good one, who knows. newegg has 450s for about $100 bucks. my motherboard is MCP61PM-GM rev:2.4. since your onboard graphics is nvidia i would stick with that.