I love posts like this, you even stated your budget and even gave your full pc specs lol. Lemme just make sure you have a free pci-e slot, and ill look up a GREAT CARD, youll definitely notice a difference in gameplay.
Just wondering, but what resolution do you play Wow at? / What resolution is your "Generic PnP monitor"?
Also, would you happen to know the maker/model of your powersupply? Getting a great video card will pretty be all for nothing if you dont have a reliable powersupply in your computer that can power it.
Here:
If you want top of the line performance, I would recommend this card at $199, the ATI HD 4890
http://www.newegg.com/Product/Produc...82E16814150359
It requires both a 6pin and 8pin pci-e power cable.
If you want the best bang for your buck, I would recommend this card at $99, the ATI HD 4850
http://www.newegg.com/Product/Produc...82E16814150337
It requires two 6pin power cables.
If you want a balance between the two, then you could go for the 4870 at ~$150
http://www.newegg.com/Product/Produc...82E16814150403
The reason why im suggesting ATI and not NVIDIA is that currently, i think they are the leading maker on the market in terms of your budget and the greatest value for your dollar, meaning that youre getting better performance for less money.
You could MOST LIKELY max out WoW and probably many other games that have been released