SLI My Motherboard will i see more fps

For sure. I don't think the x8 PCI-E lane will bottleneck too much. Definitely do it! GTX260 in SLI is a beast of a setup!

Yes, in higher resolutions it will. What resolution do you game at?

Whether it's x8 or x16 slot matters very little in performance (there's a comparison somewhere, too late to google right now).

Just saw you have a 19" monitor...is that 1440x900? SLI really only helps in higher resolutions, such as 1920x1080 or 1920x1200 or higher, maybe 1680x1050 even, but probably not so much at 1440x900.

You'll notice a good boost in preformance. The x8 slots doesn't bottleneck many GPU's out to date, some few games can be a bit limited by x8 in some settings - but still you'll see a good boost with 260's in SLI so you should definietly go for it if you can.
You will see better preformance with low res also, but the higher resolutions the more it's worth it. 19" is a bit small, but if your thinking of buying a bigger monitor any time soon at least you'll be prepared for that. Anyhow you'll have a difference in preformance, but it's more noticeble the higher resolutions you play at.

Thanks for all your replies guys, i just want more fps in some games i play like GTA 4 (quad would help) , crysis. what could i do to get more fps.

get a bigger screen and then get another card.

at the moment your screen is too small to take advantage of the SLI

This my be a stupid question but if i get a 22-23'' monitor will i see more FPS.

It's not the size of the screen, it's the resolution, though the larger the screen, generally the higher the resolution. At a higher resolution, yes it will help dramatically when you start cranking up the eye candy. I would get a bigger monitor with a higher resolution now, since your GTX260 can handle it very well, and then SLI later on down the road.