I have floor registers for my HVAC system (geothermal, 2 stage unit that covers 4 floors - basement/1st floor, and 2nd floor/attic). The registers were mostly placed in the locations of the radiators that I had removed, so a lot of them are underneath windows and in other places where I'd like to have furniture. I'm considering adding plastic pieces to redirect the air, so that it doesn't all blow directly onto a table, for example, and instead circulates throughout the room better.

My question: are those air deflectors effective in situations like this? If so, are there any particular brands that are particularly good or bad?

Thanks!