My brewing system consistently yields 70-75% efficiency. Sparging with water temperatures that are higher than 168F shouldn't present any problems with tannin extraction either, that reasoning seems to becoming more and more of a homebrewing myth lately.
Right, the more I read, the importance is more on the PH of the water than the +170 degrees temperature, where tannin extraction is concerned. Sparging with lower temperature water shouldn't propose any issues.