Im bouying a new video card

You have to upgrade your PSU as well.However if you really cannot afford the PSU, get a HD 5750 or HD 5670.

if you can't upgrade the psu, then your video card upgrade will be limited, like Tamz_msc said go for a 5670 or 5750, the 5750 will be a little bit better but without a solid 500w or more psu you should not attempt to run anything much higher than that... what is the exact make and model of your psu, or if not what are its specs? (open case and read off psu) you might be able to get away with a 5770 but that might be pushing it on a generic 500w if it not truely providing the specs that it listed since it has no efficiency rating... but knowing nothing about your setup I would either get a 5750 or gt 240 which also requires low/no power, here are some ideas, I know you are argentinian but here aer some examples of us prices so you know what kind of price scale to look for in respect to your countries dollars I guess....


XFX 5750 $98 AR
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

GT 240 $55 AR:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
304&cm_re=gt_240-_-14-125-304-_-Product

5670 $65 AR:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

the most powerful card is the 5750, then the 5670, then the gt 240 but the thinng about the gt 240 is very low on power consumption, really so is the 5670... so the choice is yours but if I were you I'd save some money to upgrade the psu...

you might even be able to pull of a 5770 but not knowing anything about your psu I couldn't say for sure, the 5770 would by far be the best card you could potentially run with that psu, definatley faster then the 5750/5670 and with your 23" the 5770 will perform better at your likely higher resolution im assuming?