I highly doubt your wireless router can be causing that effect, have you tried moving it to see if it's a problem. How old is your speaker set up? Maybe it's finally giving you a death cry.
Is the thumping coming from your sub, or your speakers?
When did this start happening? Do you remember doing anything before it started happening? Have you tried unplugging everyrthing, and re-plugging it back in?
Also have you tried the speaker system on another computeR?
This was going on with my old PC too. Didn't try to unplug each lead itself to see if one might be bad.