I currently have a pair of GTX 570s running in SLI. Mobo has a 3rd pci-e slot that is currently being unused.
I have an 8800GT just sitting around and it's a nice single-slot card that won't take up much space. Power supply (1000w) is not an issue either.
Will there be any benefit to adding the 8800GT and dedicating it to PhysX? As mentioned, I have the mobo space and power to do it, as well as a spare card lying around so there aren't any logistical issues to overcome or extra $$$ to be spent. In other words, sans the higher power draw, it appears to be a mostly "free" option.
The question is whether there will be any real benefit - either now or in the future.