The biggest reason why I use the regulator upstream, at the compressor is that is where it is on the compressor. Ideally, I would use some metal pipe to cool the air down, as close to the compressor as is possible, because the hotter the air is, the more heat it will transfer into the pipe. For me to use a down a down stream regulator, I would have to go and buy one. I gpt lucky. The second tank was just given to me.
Remember the title of this thread had the word "inexpensive" in it.
I like the idea of the wall mounted manifold to cool the air.