Hello all,
 
I had 3 9800 GTX's in SLI, but one of them finally crapped out after 3 or 4 years.  So now I am left with 2 and an open slot.  I play BF3 and I have two monitors so the two 9800's show their age a bit.  What is everyone's suggestion?  I don't want to render my two cards useless, so maybe I can use one/both of them for PhysX and buy a whole new card.  I don't want to buy the most expensive card and I also don't want to buy some arcane card that is already outdated.

Max killz

you could pick up a GTX480 for about $200-220 or a 560Ti 448core

 
Or even just a regular 560 Ti.
 
In any case, keeping a 9800 for PhysX isn't an awful idea, but remember that most games (including, for example, the mentioned BF3) cannot do anything with that.  Pretty much just the recent Batman games and 'Alice: Madness Returns', actually.  Oh, I guess Planetside 2 when that comes out.
 
Not much!