Upgrading help - old sli or new single card?

[alexisonfire]

Looking to upgrade my graphics card within the next few months, but don't have a lot to spend. I've scaled it down to two options, which are..

Go sli with the card i've already got or upgrade to a 7800 and sell my current card.

So

2 X ocUK Inno GeForce 6800 GT 256MB DDR3 TV-Out/Dual DVI (PCI-Express)

OR

1 X OcUK GeForce 7800GT 256MB GDDR3 TV-Out/Dual DVI (PCI-Express)

Advantages and disadvantages please

 

[alexisonfire]

Hmmmm, lets pretend the two 6800's and the 1 7800 give the exact same power output...apart from cooling issues with sli, would there be any advantages having two cards over 1?

 

[alexisonfire]

There must be some things sli can process faster than one graphics card, no? Someone must know the details