"I held off then because the D800 was coming and was sorry to see that its low light performance is the same as the D700"
Are you serious ?....are you shooting at night with no moon or something ? LOL The D700 is absolutely fantastic in low light...so far ahead of the D90 its ridiculous ! Useable ISO 6400 - how much more do you really need ? Sounds like the D4 might be the better option if you need even better low light performance.