There are fanless coolers like the sonic tower
that will do the job but for what they are, its a very expensive way to go, they're also huge and impractical and don't particular cool well. You'll find that stuff like your hard drive and PSU fan are making more noise then your CPU cooler. Best...
Its a hugely complex process. Turbo engines run at a much lower cylinder compression ratio 7.5:1 while NA engines will run closer to 9.5:1. If you take teh turbo out with out rasing the compression ratio (this involves using different pistons) the engine will run like crap. Also you would need...
Bench marks are useless they will show that one chip is 1% or 2% faster than the other at pure number crunching. What counts is real world performance and in this case the difference is will be entirely unnoticeable.
In reality you probably wont notice a speed difference between the 1.66gHz and the 1.73gHz, as long as you get the 2GB ram model it will run windows vista and any application you want for ages to come.