I didn't read all the answers, I was just browsing through here while eating lunch, decided to post.

 

First off a common misconception about video cards is if they are a 1gig card they are going to rock your socks.  This is simply not true.  You can get one for around $100 and its going to be alright, but for graphic intense purposes I would really consider investing.

Nice power hungry cards are going to require additional power in most cases.  If you walk into Best Buy and purchase a computer off the shelf its going to be great for writing emails and surfing the web and all things that Jane Doe needs to do, BUT for high end graphics and gaming its not going to be a prize catch.

First off you are probably going to have to replace your power supply.  When I bought this computer last year it came with a 450watt power supply, simply not enough, I think I put an 850 watt or more in it, I don't remember exactly, but it is pretty decent.

So I already had an Nvidia 275 BFG card, so I threw that in there, but eventually a few months ago I replaced it with an Nvidia 400 Series, I think its a 1 gig, and it cost me somewhere between $300 and $400, but its completely awesome.

I play a lot of games as well as 3D and run PS, so its extremely important what card I have.  It renders pretty quickly, and because I have also purchase a new LED backlit monitor my frame rates in games are over 100 or more at times. (take WoW for example) regular LCD monitors will not go over about 60, its just the way they are.

 

You need to have the power supply to run the card, as many cards will come with an additional power connector that will drain from the power supply.

Also remember that Nvidia is just the name, there are many different companies that manufacture Nvidia cards, so if you are looking at two cards that are Nvidia that seem to be exactly the same except one is a higher price its probably because its a different manufacturer, and what you should do is compare the two different manufacturers, read about them online and see which has the better reviews.

 

Just my 2cents =)