Has Lou shown any signs of being un-Able to pee? Any squatting but not peeing, any straining, unusual pacing, is he acting sick, is he eating/drinking normally? Male cats especially are at risk of developing serious life threatening issues when there is an obstruction (stones/crystals) that physically prevents them from peeing. If this is the case he needs to see a vet now.
I agree you need to put the litterbox back on the first floor where you had it initially, give Lou time to get used to it being back there again - ie don't move it again for about a week. Next week you can move it closer to the basement by about 3 inches at a time, what you want is slow gradual changes, it may even take 3 months or more before he is comfortable with the box being moved to the basement - that's okay as long as moving the box doesn't stop him from using it. Some cats are more sensitive to changes than others, and the noises in the basement may never be okay for some.
Why not leave the box in the bathroom on the first floor?
Avoid biting when a simple growl will do
The Spirit Lives As Long As Someone Who Lives Remembers You - Navaho Saying
Vindication ~ For all those pets who became sick or lost their lives from tainted pet food