2 8800 GT in SLI with 8?00 in third slot

Hi just ordered asrock 3 slot SLI M\B , I have 2 BFG 8800 GT to run in SLI, id like to try using 8?00 card in third slot to handle Physix,(as i have read its doable)
several questions for the Qurus:
1) i have 3 way SLI bridge do i need to use it?
2) is it better to run a 512- 8600 as my Physix card or will i get good results using 512-8400 card. As the 8400 card are 1/2 the price of a 8600 card, will i only get 1/2 the juice?
Thanks in advance, Glad this brain trust is here has helped me countless times over the years.

 

You just install the card in, you dont use a SLI bridge for the card you gonna have setup as phsyx. As for which card would work better I guessing the faster one.

 

Lemme clarify all your doubts.
U just need to connect the SLI bridge to the two 8800s and not to the 8600GT.
And currently you cannot use Multi GPU setup with SLI.So if you buy a card it becomes useless as current drivers don't support multi GPU+SLI setup Physx..Hope that big bang drivers have it fixed.
And believe me you need atleast a 9600GT to get good performance in Physx as you can see in the thread i have posted.Buying even an 8600GT will be a waste of money as your sli setup GPU physx will out perform the 8600GT PhysX by miles.