video card questions

OK...i have some questions to ask

1) When will the new 9800 GTX+ cards come out?

2) What is the difference between a stock version video card and the overclocked version video card? The overclocked typically is 30-40 dollars more. Can't you just overclock it on your own when you buy the stock version to acheive the same settings? Or can the overclock version be overclocked better than the stock version?

3) I'm all ready to buy the parts for my gaming computer and am stuck on which video card(s) I should get. I have a 24 inch monitor and want to run it on 1600 x 1200 resolution. Im buying the 790i motherboard and want to SLI for sure. Dont know if I should go with 2 x 9800 GTX's, 2 x 9800 GTX+'s, 2 x 9800 GX2's ( though getting really expensive), 2 x GTX 260's, or go with a single card for any of those and add a 2nd later. I dont want to throw down $1000 for something when I got get basically the same thing (FPS wise) for half as cheap. I know that certain video card configurations are better for 1600 x 1200 resolutions. Any feedback on this?