willland

 
Many have described them that way but without the Cornwall's lower extension.
 
 
I have heard quite a few on this forum mention HK/Heresy combos.
 
 
For HT a definite no.  For most music you could get away with it if you take advantage of available boundary gain but much better(deeper Hz) with a quality subwoofer. 
 
 
No low bass but midbass punch is great, IMO.
 
Bill 

Kahnoleary,
 
Welcome to the forum.
 
The RF-82's "may" overpower the RC-52 if your room is on the large side and your seating position is more than say 11ft away from the center.  Now the RC-52 will not be a "perfect" match under any conditions.  As far as the RS-42's, you should be fine.
 
Bill

 
Great choice.  I have a previous generation C542 and it is the best sounding CD player I have ever owned, and that is compared to some good ones like a Cambridge Audio 840C and Denon DCD-3520.
 
Bill

 
This is the best I could find for you.
 
Onkyo TX-SR706 
 

 
 
Now I know we are not talking exactly apples to apples here considering the 706 preceded your 717 by four models(707,708,709).  But, the weights of each are about the same(706 = 26.9lbs vs 717 = 26.7lbs) which may indicate a similar performance with the same or similar power supplies.

 
 
First, welcome to the forum.
 
Second, most models of Klipsch speakers are very revealing and the quality of recording will dictate just how the sound will be conveyed.  Those titanium compression tweeters can be an ally as well as an enemy when poor recordings are played.   I doubt your Cambridge Audio 751BD is the culprit because I love mine and am very impressed how it reproduces CD's.
 
Maybe try toeing your 83's out a bit more so they will shoot about 6 inches off plane on the outside of your ears in your main listening position.
 
I absolutely adore my RF-63's and some of the finest music has come to my ears from the horns of those babies.
 
Go to this website and let it be your reference stop for recordings choice.
 
 http://dr.loudness-war.info/album/list?artist=eagles&album=
 
As you can see from the chart, the "remastered" recordings are not the ones with the best dynamic range.
 
Bill

dDave,
Welcome to the forum.
Your Onkyo TX-2500 is a 70's vintage stereo receiver that produced 30w/ch at 8ohms and 40w/ch at 4ohms. With that said, 30w/ch(stereo) back in the 70's is more like 75w/ch(stereo) in 2014, from my experience.
Your new(to you I am guessing) Marantz SR5001 is a 7.1 channel AVR that is spec'd at 90w/ch@8ohms in stereo mode but most likely only puts out about 40w/ch with all channels driven. The upgrade you may be realizing is that you are going from a stereo receiver to a multichannel receiver which is necessary for HT, not really much of a power upgrade except in stereo mode(90w vs 30w).
Now if you were to add the Citation to the mix, then that would be a significant power upgrade. Let the Citation drive your front soundstage(left--center--right) and let the Marantz drive your surround channels.
And no, 300w/ch will not harm the RF-52's unless you get crazy-stupid with the volume knob.
Bill