All three of the speaker brands you mentioned are very good choice with your wonderful new Elite[good move] and I would add Monitor Audio to your list. I love my Elite/ MA system and take a look at the MA Silver series. I use the Silver 2 for mains, the Silver center and the Silver1 for surrounds. Very nice.
This is just my opinion, but I would say with a receiver as an amplifier, you will get the most out of speakers with a nominal impedance of 6 or 8 ohms (as opposed to 4) and sensitivity that's 88db or more, specially if you plan to drive more than 2 speakers with the receiver. I seem to remember reading that the Polk Lsi, while an excellend speaker is 4 ohms, and not easiest load, but I could be wrong. Once you've narrowed down the list, check the specifications for impedance and sensitivity (the sensitivity is somewhat exaggerated by many manuf. so beware.)
I have the Polk LSi15's they are awesome, but being a 4 Ohm speaker my Amp The HK AVR 8000 gets smoking hot. If I were to do it again I would try to find something in the 8 ohm and 90db sensitivity. I would look at the Monitor Audio. I am setting up a 2 channel in a listening only room, I am going with the MA silver 2's, really nice sound. Good Luck.
I heeded Seth's advice and went with an 8 Ohm speaker deciding to purchase the Boston Acoustic CR77's with the CRC7 center. Instead of going with the Velodyne or Hsu Research sub, I really liked the sound of the B&W ASW600 sub and purchased that too. I should have all set up in my new media room by Turkey day so I will report back as to how this combination sounds in my home. If not - I can always return.