Originally Posted by
DougMac
This is speculation on my part, but I think I'd categorize the Sierra upgrade as subtle and the sub upgrade as huge.
The Rythmik is in a different class from the Polk. I think you'll hear a tighter, better defined bass with music. Where you'll really hear the difference is with HT. The Polk only goes down to 35hz while the Rhythmik will get down in the low 20's. There's plenty of movies with content that low. A sub that can play it really adds a lot.
You'll be hard pressed to find another sub at the Rhythmik's price point that does everything as well. There might be some that play a little louder but at the cost of control.