EggXpert

I don't know about any headaches tied with SLI, considering It's just a click in the Nvidia Control Panel, or it is for me anyways. A true SLI set up involves 2 or 3 PCI-E x16 slots, a SLI chipset like the 500, 600, 700 series, and 2 or 3 nvidia cards that are SLI capable, and a PSU that can handle it.

thanks for the info guys. i asked before but ill ask again, can my PSU(linked below) power the 9800GX2 safely?

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341010

Like ATI with their Crossfire not all games are supported for SLI in the drivers and then you will be playing as if you had one 9800.  Check the reviews to see if your games are supported.  (many current ones are, but not all, and older games are often not supported and in rare cases performance goes down below a single GPU of the same power)

I would suggest you visit a SLI based forum or two and read up about SLI or Crossfire to see the pros and cons.  I have been in computers since the TI-994a days and I would just get the fastest single GPU card I can afford and avoid the multi GPU headaches.

Also make sure you have enough CPU power and a big enough monitor to warrent all this GPU power.  If not you are just wasting monies.  

 thanks for the info, but im still wondering if my PSU(link above) can run a 9800GX2 or a GTX260.

thats good to know. but again, can my PSU (linked above) run the 9800GTX or GTX 260?

No I wouldn't suggest using a 500W PSU to power that Rig with a 9800 GX2.

Merging threads. 

its a 600W PSU. ill link again.

 

 http://www.newegg.com/Product/Product.aspx?Item=N82E16817341010

600w is min, if u want to add nething or OC you'll need some more juice. if your not on a tight budget id at least get this. If u wanna SLI more than one actual card u might need at least a 800w.

I don’t think that he will OC at any time soon when he does not know too much about SLI as of yet and learning.

Correct me if Im wrong but I'm also pretty sure that since the card is in an SLI setup you will only be able to use one monitor at the cards full power too so make sure you dont ever need multiple monitors