I've never heard them, so can't really give you an honest answer on that. However, Polk is enjoyed by many. These seem to be pretty sensitive and an easy load. They're rated for 200watts-rms, which means they're likely excursion limited for that extra low end response.
I think your best move now is to get the center channel (CS series) to replace the Klipsch. Lots of the content from movies comes out of the center channel, so your really short changing yourself there. The rears, if/when budget allows, would probably be best to be matched as well but that's not essential.