Re: Upgrade worthwhile?
In that case buy the best card you can afford where you live.
If the HD 4870 1Gb is cheaper than the GTX 260 Core 216 where you are, consider it. I really can't recommend cards with 512Mb ram at this stage in the game. While they can play some very demanding titles fine they will hitch or stutter much more than cards with larger ram amounts. So their FPS might look fine on paper and feel like garbage in a demanding game.
Also make sure you're buying from a company that has good support in your country.
A manually overclocked GTX 260 is a nice move from an 8800GTX. I used a manually overclocked 8800GTX from their release until the GTX 260s hit. I definitely noticed a difference @ 1920x with AA active. 8800GTX is still possibly the best card nVidia has ever made.
The new cards are good and they are more of a modest evolution than revolution.
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