I did have two D700s, but I've just changed one to a D800 (mainly for studio work). I'm not looking for wedding work, but I'd be happy to do one with a D700 & D800. You need to adjust WB a lot due to the dramatic lighting changes in a wedding (which I appreciate you know), and I assume (the mother of all fuckups) a different body wouldn't make too much difference. Of course the lenses are important, but he already seems to be going for decent lenses. The main benefit of the D300 over the D90 is the extra buttons etc to make changing things quicker. They use the same sensor, and the D90 came out later didn't it? It's about £1150 / £1200 for a mint D700, so I'd upgrade to that level or better asap, and 2 * D300 would just delay that.
Ah, I thought you were going to say a dozen or so. I know the D200 was a good body, but that's quite a step up to the D3, so maybe that's why you gave up the D200 quickly
I recommended the D300 for budget as Im really into my lenses. Over the years ive gone from D2Xs, 20D, 40D, 1Ds MKII,, 5D. I could go on. My point was in regards to the dynamic range on each body was so different that I would always want to shoot with the same cameras. I dont really care too much which body I use but if someone is looking to build up a decent system then I was saying invest in the lenses and change the bodies as and when.
Love to see some of your studio work?