I'd find a local dealer with both brands of speakers and test them out to see which sound you prefer from Polk vs Infinity. My home theater is made up of the Infinity Primus line and I really like the sound. They aren't pretty to look at but for the money, they are great quality for that price range. Their sound is considered on the 'bright' side I think.
Polk makes some more aesthetically pleasing models, but I'm not sure Polk is a great value for the sound quality.
There are SO many speaker companies out there though. If you can, try to find demos of PSB, Aperion, AV123, B&W, etc.
im from the mid 80's hi-fi gen. i own infinity kappa 8 speakers. they are over 20 yrs. old. am looking for different sound. compacts are of interest. im thinking polk Rti/A1. anybody have an opinion?