Renting a lens for 2 (or even 3+) weeks might be cheaper than renting a Nikon and lens for a day or two. Here are four great options right here:
Rent professional cameras or camera lenses for Canon, Nikon, Sony, Olympus, Leica and Pentax
Furthermore, I believe the K-x can still outperform most other camera (such as the D700) in low light. Plus the 16-70 sounds a bit short, and it's a DX lens so you won't even get the benefit of an FX body with it - might as well use an APS-C Pentax anyway with one of these superior lenses.
In fact, the only downside to this plan is that after renting any of these you'll want to own it!
I can personally vouch for the last 3, all of which I've owned and still own (or replaced with an equivalent+ older Pentax model).
Last edited by DSims; 01-08-2013 at 06:52 PM.