Just to be clear... the D810 and D850 have a small edge over the D800 because they can go down to ISO 64 and gain some dynamic range from doing so. At ISO 100, they're all very similar. The Df/D4 (same sensor) and especially D3s have 1-2 stops (respectively) less dynamic range available at ISO 100, although they overtake the D800 above ISO 800. The D800 also gives you more pixels to play with, obviously. The D7200 holds up remarkably well considering its sensor is less than half the size of the D750 and it's receiving correspondingly less light, but I've not often heard people claim it's better in low light. I would say it's an example that modern DX sensors are a lot better than you might expect if you're used to old ones, though. You would struggle to buy a new full-frame camera for the £1000 budget, though (although you might manage it from Sony). So if you want new, unless there's a big dip in prices when a D750 replacement appears (and rumours are that UK Nikon prices are about to go up), you might have to look at DX. Just to be clear, most pre-AI lenses won't mount on any full-frame Nikon dSLR other than the Df, because their aperture rings will foul the AI follower tab. The Df is the only body that allows the tab to be folded out of the way. You can solve this by having your pre-AI lenses converted to AI, but obviously this means modifying them. "Early 70s" suggests you might have some pre-AI lenses, which might point you strongly at the Df, but it's a very esoteric camera and I'd think carefully before committing to that. Bear in mind that many low-end DX cameras can work (without metering) with old lenses as well - they just don't have an AI follower tab to foul on anything. The D700 has a very strong AA filter (pixel peeping the images are quite soft unless you sharpen them), it's about a stop worse than the D800 as ISO increases, and it's lacking a lot of dynamic range at base ISO - in addition to having only a third as many pixels as the D800. Plus you'll be looking at third party battery replacements - Nikon discontinued them due, I believe, to regulations about exposed contacts. The D700 is a lovely camera of itself, but the D8x0 range are a large step up. I found myself having many autofocus problems with the D800 just because I could see when I'd missed focus, whereas on the D700 everything was a bit soft anyway. And yes, I suspect a lot of people stuck to the D800 rather than upgrading to the D810, since on paper they look similar. Those I know of who upgraded found it worth it, though, so if you can stretch to the D810 I can vouch that it's worth a premium. That said, if I'd got more trade-in money offered for my D810, I might well have picked up a cheap D800 as a backup system; now I believe the price premium for used ones is relatively small (a lot of D810 owners will have upgraded to the D850 too), so I'd take one if I could to avoid the D800's niggles. The D810 has somewhat more reliable autofocus (though it's a little worse in low light), better live view behaviour, highlight metering, some compatibility advantages, etc. - none of which sound critical, but all of which stack up.