I am thinking of upgrading from my D90 to a D600 and am seeking your thoughts and suggestions

I haven't sold anything on eBay etc so would prefer to trade in my D90 and a 35mm 1.8 Lens
to reduce costs as I only need one DSLR camera, got one quote $320 D90 + Lens

Checking D600 prices it ranges from $1900 Gray-market to $2500+ at Melbourne Camera retailers

I'm not totally confidant in gray-market and warranty they offer, nothing went wrong with my D90 but
I am a pessimist and usually expect the worst