Temperature of the mash is important, but no way am I worrying about tenths of a degree. If a mash calculator tells me my strike water should be 166.7F, I'll be shooting for 168F. Preheat your cooler with a couple of gallons of water and use an online mash calculator to figure your strike temperature based on the temperature and amount of your grain and desired mash temperature. If you lose a degree or two over a 60 minute mash, no big deal. For sparging, I try to do a single batch sparge where I collect half of my boil volume with the first runnings and half with the second. See http://hbd.org/cascade
dennybrew. Finally, with batch sparging I am starting to believe that the temperature of the sparge water is not really that big of a deal. You don't really need to mash out and are really just rinsing the already converted sugars out of the grains.
Even with your heat stick you would have to heat your strike water higher than the mash temperature because the grain is going to lower the temperature of the strike water. Assuming the heat stick didn't cook the grains right around it, you would still have to wait for the heat stick to raise the mash to the desired temperature.
In a nutshell, yes you have to heat your strike water above your desired mash temperature, but you don't have to make it complicated.