I found a well-preserved, pre-owned Nikon D3s today (Thursday) at Houston Camera Exchange. Apparently the anticipated nearness of the release of a D4s successor has caused the asking prices for the D3s to drop, as this one was priced a bit lower than a previous D3s, at the same place, in far worse condition, with ten times more shutter actuations, a few weeks ago. ( <22K versus >210K, if I remember correctly,)
Following so soon after some substantial recent lens purchases, this will require some painful sacrifices, probably one redundant high-end Canon lens, and/or two or three firearms, but a camera that can "see" in the dark, notably better than a D700, seems worth it. With the night shooting I do at work*, I believe this purchase was justifiable for more than just personal shooting. Depending upon the source, a D3s should represent a half to a full stop better low-light capability than a D3/D700. I will start to confirm this tonight or this weekend.
This purchase also reinforces my recent trend toward FX Nikons, while also using cropped-frame-sensor Canons. I still love my new 7D Mark II pair.
*I do not claim to be a "professional" photographer, as I am not in the business, but do shoot some quite important images as part of my duties as a public servant.
Canon 5Ds R/7D2/7D/5D/40D/1D2N/M3; Nikon F6/D3s/D700/FM3A/1Dx/Coolpix A. Lens selection undergoing changes; some favorites: Zeiss 2/135 APO Sonnar, Canon 100mm f/2.8L Macro IS and 135L, Nikkor 14-24/2.8G and 24-70/2.8G.