If you cannot be without a camera while yours is in the shop,why not rent one? Unless you are looking for an excuse to get a new one. In that case, I think the D600 could be a good choice, unless you want to stay with DX.
My D40x now lives with my son and his wife, and I've been thinking about a D600 - just haven't figured out if I really "need/want" it.
Lens compatibility is something to think about - I "need" more FX glass!