I don't see an upgrade - any of them - making an enormous difference.
The D5000's LCD isn't shabby, and if you're looking for clarity as to the sharpness of the photo, zooming in on the pixels ought to do that pretty well. Even the older and much smaller LCDs do this quite well (I'm thinking of the D100 here).
"ISO clarity" is literally true, but in practice may not be that relevant. You're shooting with VR lenses and flash - the upper limits of the D5000's sensor shouldn't really be in the way. Seriously, how often are you at ISO 1600 or above? And if you are, how often is that due to trying to avoid the use of a tripod? (If you had said sports I'd be more inclined to think high ISO is an issue, but I don't see sports in your description.) Also, how are you evaluating "noise"? At 100% zoom?
Added pixels will likely do you no good at all. Surprisingly perhaps, you won't even see the difference if you go to 24mp (ie the D3x), unless you're doing some printing that you didn't mention. The places that lots of pixels help are either (a) cropping a lot, which I'd argue is really a lens problem and not a sensor problem, (b) making large prints, and (c) ... well I can only think of two. The D5000 is already 12mp, with which you can make at least a quality 24 x 36" print, assuming good lenses, excellent technique and good post processing and printing skills. Going to 16mp in the D7k will be essentially invisible until you get to the large prints. My definition of "large" is 20x30 or larger. An 8x10 at typical print densities actually throws away information from a 12mp file, and an 11x17 is about native resolution.
I can't comment on video.
A D700 is clearly not something that is a great deal right now. It buys nothing in resolution (it's 12mp too), it gets you higher ISO - but a D7k will do almost as well for half the price, and... little of functional value over the new DX bodies. (There are definitely differences, but they're things like bracketing intervals, AF-on button - stuff that you're not encountering yet.) For a lot of money more. Of your kit, if you switched to FX, the only thing you'd save is your flash and the 70-300. It would also cost you at least $3000 even if you got minimal lenses. With something like a 24-120/f4 it would be more like $3400.
My advice is to spend the money on opportunities to make photographs (you're already investing in the area that counts the most, which is improving the photographers). If you're wanting to spend on gear, I'd go for a really good tripod and head (probably a lot more than you're expecting), a macro lens (probably not very expensive - I don't see the need to spend more than $450) and possibly an ultra-wide lens. A good tripod will do more for sharpness than anything else, and the great thing is that it applies to all lenses and cameras.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!