I have a set of the polk audio 651 speakers and they sound great to me. My question is do the infinity speakers sound better than they do & would it be worth switching over to them? I know everyone has their own opion but always looking for better.

 

Both speakers are great speakers. . I have both and I can't honestly say one sounds better than the other. . . Different Yes. Better No. Depends on your ears and what music you listen to. I presently run the infinities because they are more durable.

 

I believe that I had a bad set of Polks. So to me the infinitys sound better.

 

I think your splitting hairs, the polks will hold there own as
Far as sound is concerned. I don't think there will be a "night and day" difference if that's what your hoping for.

 

same level speaker from reputable companies
If your pair of polks is not defective... then you will likely have to spend 3 times as much for a better speaker. I've had good luck with their db series in a few "soccer mom" systems.
That being said the older kappas are awesome as well.
If they sound great, then turn it up