The last sub $300 Polk I listened to (R30 tower at $299) did not impress me at all, although they were better than my old $80 boombox. I preferred the sound from the bookshelf M3.

The M3 is a speaker they wouldn't need to upgrade from unless a future budget allowed them to. They even sound good with my crappy RCA HTiB Rx, so, depending on what they have now, a new receiver may not even be required.

M80s/VP160/QS8s/EP350; M22s; M3s.