VR I's tend to sell for about $1500 on ebay from local sellers .. so if you have the $1400-1500 to spare then definitely aim for a Nikon VR I version as your first priority.

BUT!! at some of the reputable grey retailers the Sigma sells for about $1100 or so, and that $400odd savings buys you a whole lotta goodies too
Sigma's local distributor should be able to give you a price match to that ~$1100 if you want to purchase through the proper channels too.

focus in low light should be fine on all three lenses anyhow and the D800 apparently has the most fantastic low light focusing ability(down to f/8 af ability, so focusing may not be an issue with any of the lenses referred too).