hang on here. i heard 8800gts320 is not good. the '320' is not good enough and higher amount is needed huh. explain this please?
The GTS will be fine for lower resolutions (below the maximum of that monitor), but 1600x1200 is the point of diminishing returns. Paul's talking about the reality that for your current situation it's fine, but try to game above that resolution you're going to have issues. Something to consider also IMO is that aliasing or AA on a 17" 16x12 monitor isn't as noticeable as AA on a 21" 16x12 monitor so the level of benefit diminishes as well.
Should you be looking at a new monitor then the bar of quality is raised and you will see an appreciable difference offer by the GTX.
Now the GTS (and likely GTX) will be weak in DX10 mode compared to their DX9 performance, but you will be able to balance settings for it, and it will do ok for while.
If you think about your spending, for what you save on the GTS, you can roll that into the next products that will liklely handle the games like Crysis, etc better.
So IMO you have two options: the GTS for someting now with an eye on refreshing by the end of the year or early 2008, or the GTX if you plan on holding this card for much more than a year.
Personally I'd recommend buying the GTS-320 for your current situation, and then take the savings and roll them into something better later (at which time buy a new monitor with the money you get from selling the GTS).