Too low of power output will certainly cause stuttering among a few other weird things that happen to your games. I am using just a little ( little compared to some of you ) Nvidia GeForce 260 OC 896 MB GDDR3 that requires 525W PCI Express power supply with a combined 12V current rating of 38 amperes or more. I am running a BFG 680 Watt power supply ( PCIe ) with four 12 volt 20 AMP Rails which combines 80 amps.
I have no stutter and never have had with this graphic card and power supply combo.
elbmek I thought you bought a much bigger card than I'm now running? The guy may have told you a 450 watt PS, but I'll give you a clue, 800W or larger in wattage would be a lot better and they will have the correct 12V power rails with the correct amperage. 450W ?? I think not as these larger two slot cards really can get power hungry.
Also check the Mfg. of some of those power supplies as some are worthless junk ( no I'm not going to mention any junky Mfg. names. ) Sometimes it is worth paying a little more and getting more. ( thumbs-up )
That's a classic case of sales reptile garbage. "Oh, your PC isn't working? Buy my stuff!!"
With a problem like stuttering in games it would be helpful if you listed your computer setup, what version graphics card drivers you are running and perhaps what in game graphics settings you are using as well. Also that power supply he listed to you is garbage do not buy it.