My PC is probably 8 years old. It's a P3 so it does have plenty of cpu power but . . .
I bought the external USB SB card just in case I'd have to try the laptop. We'll see. If I still hear noise it's probably a connection, as you say.
I do have the horn sub on casters. I was thinking ahead on that one.
It is located pretty close to the front wall in a corner. I don't have the room mode calculations I made with me so I haven't yet compared those with what I'm getting.