you stated ur not going to use big and bright light like in the picture (that was just a test) but do you really think a led light or two is gonna give you the extra light you seek ?? im not sure if it will. it has been my experience with led lighting is that is it more of a ambiance soft light type thing versus actually using it to see, Esp one a old back road stuffed behind a grill or under the car.
but its ur car/time and money give it a shot and see if it suits ur needs and liking
good luck