Used D700 or new D7100? What would you buy?

I do a number of portraits throughout the year and a few weddings. Here in UK I always seem to be fighting for light esp in dimly lit churches! My D300s broke and I was just given a full refund by John Lewis (incredible service!!) as they were unable to replace it. So I now have £1,000 to spend body only. I have several DX lenses and a 50mm1.8D and 28mm1.8d. The jump to a D700 would initially limit my lens use but I think I can afford the 85mm f1.8G as well.

Can't afford the D600 but the price of a good used D700 is much the same as a new D7100.

Whilst I am tempted by a good used D700 it only has a single card slot and I have had two critical card failures.

The D7100, for me, seems to combine the AF system of my beloved D300s with increased ISO. On paper it would seem to suit me very well. Anyone any ideas how noise at high ISO, ability to grab focus in low light is likley to compare between these two cameras?

Any suggestions?