I live a LOT further from Sioux Falls than you do (in Sioux City - 85 miles away) and get an excellent HD picture from KELO, KSFY and KDLT. The Sioux City channels are expected to have a full-power signal some time this summer, so you should be able to get both.
Using a ChannelMaster 4228 antenna and a 7775 or 7777 amplifier you should get an excellent picture from distant stations. One problem for you is that the 4228 antenna is extremely directional, and while you might get a good signal by facing north/south, you might find out that you need to point it more directly NNW towards Sioux Falls. Sometimes you can carefully tweak the pointing of the antenna to get several strong signals from slightly different planes, but then again you might have to choose either Sioux Falls or Sioux City.
Use the best UHF antenna, the best UHF amp, and the best coax cable you can afford to get a great signal. Good luck - been there.
In theory there is no difference between theory and practice. But in practice there is.