Here are my review of the Klipsch RP-160M since I've used them:
*Very, very clear and good treble. Exactly what I was hoping for.
*Detailed sound with good separation of instruments and different sounds.
*Clear dialogue in movies with lots of action and so on.
*Awesome vocals, truly, in all kinds of music genres.
*I am not thrilled with the base, not the fastest and a bit soft. I´m not feeling that this is the most balanced base, to put it mildly.
Though, I'd say if you want to play loud and listen to rock or something similar they are, may I say, fantastic. The guitars, the vocals, just amazing.
In theory the new vented tweeter in the 600 should be a little better, but on the other hand they're pretty similar (here's a comparison). How much better, I don't know though considering they both are capable of a 1500hz crossover. Each speaker is going to be the sum of it's parts and if the crossover also changed, you probably should listen to both if possible because there is likely an effect on the voicing.
But I must agree with MiddlemanOne. RP-15PM is a charm comparing to these two. Got them since I got tired from all the wires. So consider trying them if you have budget (here and here are some reviews on sounding and specs).