Can you put a power mannager on the Video card?

Well i have a friend who is having a small computer company build him a computer and what is going into the machiene concerns me.

He is getting a SLI Motherboard and getting 2 Nvidia 8800GTX's. now this mobo has 3 PCI-E Slots. and what he told me is he is having a ATI X2600XT installed in the 3rd slot.

and here is how he wants to run it. basicly he will be having his main monitor running off ov the 2900XT. and the guy that is building the computer is saying that the SLI'ed Video cards will basickly interface with the ATI card (somehow) and increase video performance.

CORRECTION!!!:: after talking to him sommore he has told me that the 3rd PCI-E card (the ATI Card) is an unknown Type apparrently the guy who is building the PC is throwing it in for free. oh yea it also has 512 Mb of ram on it. and thats all my friend knew.

the third card wont work while the other two are working, it needs to be the same type as the nvidias... sell it on ebay or somthing

edit: thats crazy isane, ive never heard of 3 SLI working at the same time!!! and why just get 512MB RAM if your already putting in the money for 2 PCI-E.... very very odd build