I live in Knoxville and have all of my life but unfortunately I saw your post too late to be of any help.
But for the next time you get to town, while not confined to just Knoxville, Firehouse subs is one of my favorite casual places to eat and Nixon's is a close second.
You'd have to drive a few miles but Litton's has some of the best burgers in town.
Doan's market and deli on Cecil, off of Broadway has great food, the only downside is there's nowhere to sit and eat, it's totally takeout.
I suppose I should add that I'm a bit biased in that I personally know the owners of both Litton's and Doan's and I used to work at Doan's.
Winston Churchill. "I am prepared to meet my Maker. Whether my Maker is prepared for the great ordeal of meeting me is another matter."