I want to buy a 1680x1050 lcd, which is fine to play older games on at its native resoloution because they dont need much power to play smoothly.
But for the most recent games i think having them on 1680 will decrease performance compared to 1440x900 resoloution.
My system is 3ghz core 2 1066fsb 3mb cache, 2gb 1066 ddr3, and a 1gb gts250. On my current 1280x1024 the next resolution below 1280 that i can play on is 1024x768, which looks fine but not as sharp as 1280.
If i get a 1680 lcd what is the previous resolution under 1680, is it 1440, and if so will it look like 1440 on a native 1440 or not as good because its not native but second to 1680?
Where does 1600x900 come into this? It's a completely different aspect ratio.
And the list horse gave is horrible since I presume the OP wants the same aspect ratio.
If you set the monitor to stretching then a same aspect ratio resolution would look best.
So set it to 1440x900.
You can overclock your GPU for a few FPS gain too.