Polk has many different lines of speakers, yours are from an entry level line. Probably an improvement over HTIB (home theater in a box) speakers, but there are much better speakers out there. Polk's RTiA and LSiM lines get higher praise for example. I'm not particularly a fan of Polk speakers but never spent a lot of time with any either, but have heard some friends' and some in showrooms; their subs aren't something I'd buy. There's a
best speaker brand thread here (and there are other threads on the subject as well) just to give you an idea of how many brands are highly considered out there and how differently everyone thinks about various brands/models. I do wonder what the other brand your friend mentioned was.....
Usually you spend as much as possible on speakers/subs and not so much on the avr/amp as that isn't as big an influence on overall sound quality (while having a top of the line receiver is a nice thing, but might be considered a bit of overkill compared to your speakers).
If you like the sound of your speakers don't worry about it, but let's just say you have much room for improvement with your speakers and subs in future upgrades (although it may go to local choices available to an extent).
Have fun!