The voltage thing is easy: don't do it. Remember power = Voltage**2 / Resistance, so the difference won't be 1.9/1.65 or about 15% more power (heat), it will be 1.9**2 / 1.6**2 or about 33% more power (heat).
Intel has really good brief data sheets as far as the processors go. The chip set data sheets are almost as good.
The processor and chip set have to agree on Front Side Bus speed, but it is between the chip set and the memory how fast that bus will go. In either case, the negotiated speed is the lower of the two, so if your chip set will only do 1.333 GHz, that's how fast your 1.800 GHz memory will go.