Newby - Polk PA12XS heartbeat

I have, what seems to be the all too common subwoofer heartbeat issue. Its certainly bad enough that it is unusable.
Based on what I'm reading, I have 2 choices, replace the board or the entire unit. I'd prefer to replace the board. And unless I can get assistance from Polk, a replacement will be other than Polk. Common sense?
The unit was originally purchased at BestBuy, Model PA12XS, s/n S120614118.
The unit is a part of my secondary HT setup in the basement and has had very little use (the kids left home years ago). The problem started a couple of years ago. Haven't been bothered till now.
Looking for any help or direction....thank you.