I have replaced my Polk Monitor 70's (whose tweeters I've blown ten years in; that's a hint) with these speakers, courtesy of an attractive Amazon offer likely related to their supercession by the newer RP-6000F. These are my impressions of the Klipsch after a week (it seems longer than that) of ownership:
My listening space is small (200sf); the speakers are used in an essentially nearfield application. Pointed straight at my back, 8 feet away. I'm powering them with an Onkyo receiver of sufficient output to properly exercise a speaker.
By comparison to the Polks, these things are not worth much at low power levels. No delicacy in their response; no real definition or separation of individual instruments/vocals.They're actually kind of muddy and lacking in that sense. They seem like the lower drivers and the horn don't really communicate, and there's a hard divide between what the two subsystems offer, I won't be playing them as background music while I'm sleeping.
OK, so let's drive them a bit harder.
O gawd, now I get it. I don't know, and can't measure, whether their efficiency is equal to the published figures, but one does not tout - or build towards - "efficiency" in speakers unless one desires their evaluation to be informed by how loud they can play music correctly. It's my impression that they can play pretty_damn_loud. The quality of these speakers is directly related to how hard you push them, and having flogged them like a rented mule for the last week I feel I can safely say that this is what they like. The harder you push them, the better they are. They're at their best at "I'm gonna get evicted" levels. The transient midrange lack vanishes, and bass is strong and tight down to the 40-50Hz level one should expect of such small drivers. I'm disconnecting my subwoofer just for the pleasure of listening to them; I'm gonna have to build a better sub than I already have to appropriately augment this setup for what I play through it.
There's a pair of JBL LSR-305's in front of me for the low-volume, delicate work I sometimes desire from speakers, and they're damn good at it. I don't want that from my "main" speakers; I want them to potentially get me in trouble. In terms of "potential for trouble," the previous Polks can't hold a candle to these Klipsch. I'm so_damn_happy I bought these. I considered Elac alternatives, but they felt like bigger versions of the JBL's which I don't need. These Klipsch are for turning my amp over "40" indicated (and they're ten digits lower than the Polks for the same SPL).
Don't buy these if your sensibilities are delicate, you love tube amplifiers, and you want to discern the subtleties of the individual instruments of soft jazz. They're not for you. If your tastes are more towards "crank them, up, d00d," well, you haven't heard your Holy Grail until you've heard Klipsch.
I'm gonna get evicted. It'll be worth it.