Milwaukee Magnum or Hole Hawg (corded). Find a used one on Ebay or at a G-sale. They're nearly indestructible.
They've been the gold standard for electricians wiring new contruction.
Yep, even at $100, it's still chump change compared to hiring an electrician to do all that work.
I wonder if the OP could use a cordless 1/4 impact driver like a DeWalt, Makita, Ryobi, Milwaukee? Because then he can use it and the charger/batteries for many other jobs (and will allow him to add other tools). I assume it's powerful enough at about 1,500 in-lb's. If he can get an auger bit with a 1/4 hex end on it. Or get a chuck adapter.
Tractor Supply had a DeWalt lithium 1/4 impact driver kit on sale for $75. Came with one battery and a charger. Great starter kit. Though the other brands are good too.