filling a port hole?

I have a cheap KLH sub that I bought form costco a few years ago. I have allready put some poly-fill in it and that helped alot. The sub sound good in 10x12 room but will filling the port holes make it sound better? I have foam sealant I could use, will that be good enough?

Stuff a sock in it...of a pair.
Roll up 1 or 2 (whaterver fit's tight) then listen to them...take it out and listen again. THEN decide if you still want to plug it up.