Is it worth buying a used Nixon D2X (still boxed and in very good condition) for �700 (camera body only)?

Personally, I don't think it's worrth that much even if it is new in the box. The reason I say this is the D300 that has recently been replaced by the D300s, generally exceeds the capability and performance of the D2X in every way. You should be able to buy a used D300 for around the same price and you'll end up with a slightly lighter camera that is faster, offers better image quality and a vastly improved autofocus system over the D2X. The only downside might be that the D300 doesn't offer a build that is quite as robust as the D2X with respect to weather seals but, the difference is negligible in all but the worst environments.