gtx560 SLI

I'm planning to buy another gtx560, for my PC, so i have a few questions about SLI:
1) Could i run two gtx560 with Corsair 800W, GS800 (65 Amps on 1 12v line) ?
2) Currently I have "Giga Byte GeForce GTX560, 1GB, GDDR5, OC", can i put "Palit GeForce GTX560, 2GB, GDDR5" inside, or do i need two 1gb GPUs (the same model)
3) Would my i5-2500k bottleneck two gtx560 GPus?

Thanks.

1) Yes that PSU will work great!
2) Yep, although you will only get 1GB of usable Vram. Better off to look for a 1GB model for cheaper, unless that is the only option. What games are you playing and at what resolution? 1GB is cutting it close for BF3 @ 1920x1080 or higher, you won't be able to run ultra perfectly smooth. Same with other demanding games.
3) Not demanding games, and if it does become a bottleneck it generally caps maximum FPS (so even in the majority of cases it doesn't matter as this will be way over the refresh rate of the monitor) - has no effect on minimum FPS in majority of games. Some intense RTS games may be an exception to this. If not already, the 2500k can be easily overclocked to past 4GHz to prevent any possibility of this being an issue.

I'm going to play Guild-wars2 when it comes out, in general im mostly playing MMORPGs, like WoW, Rift etc...
P.S
I'm playing at 1920 x 1080.

Ah I believe 1GB should be plenty then. The 2GB card *should* work in SLI in the second slot, as it will just use 1GB instead and match the clocks of the primary card. Again it is probably less hassle to just get a 1GB card to match it (as there will be no difference) or go with a single card.

I believe WoW scales much better in SLI now than it used to (http://www.tomshardware.com/reviews/geforce-gtx-680-sli-overclock-surround,3162-9.html) although if you are experiencing low FPS then this might be due to a CPU bottleneck (in populated areas). Overclocking the CPU will help here!

The additional GPU should help in Guild Wars 2, it seems to be a bit more demanding in terms of GPU versus WoW. Although as it isn't released there are no firm numbers or benchmarks.

Thanks .