I have a full 5 speaker set up of RC speakers.  I have isolated a overheating problem in my denon 2807 that outputs 110w per channel (it shuts itself down) when playing the RC 70's at +3db for extened perionds (20min to 40mins)  this does not happen when using my polk Ri10 at +10 no matter how long I play them at this level.  Any body have idea of the cause and or work around.  I love the sound so don't want to switch but also think that this problem will not be able to be reproduced by Denon if returned under warranty and may have better luch under the sounds around extended warranty after the manufacturer ends.

What would be the benifits off using the pre amp outs to another amp.  I know nothing about this?

I'm running a very similar setup and have never tripped the protection circuit of the 2807 before.  It's possible I suppose since you are driving them insanely hard (as in: CAN YOU HEAR ME!?!? ;) ).  It's more common that a loose fray from a speaker wire is causing a short which has the same protection-circuit effect... have you double-checked that?  You can't really compare them to the Polks... different speakers = different impedance curves. 

 If you are over-driving it, you have 2 options really: you can make sure your subwoofer is handling all the frequencies below 80 (maybe even 90) Hz.  The RC-70s should be set to "small" in the speaker setup.  Those sub-120 frequencies are usually the biggest current-suckers.  With the subwoofer handling them alone, you can have bass being reproduced by the best speaker for doing it in the best location for creating it while the 70s can use all the Denon's juice for producing the sound they're best suited for from the locations those sounds should be coming from.  It's a complete win situation and you shouldn't have things set up any other way. 

 
If that doesn't work, then - like you say - adding a dedicated amp is really your only choice.  You'd probably only need to add a 2-channel amp to drive the 70s.  The Denon should happily handle all the rest.  Rotel would be a brand you should be thinking of.  When you hook that amp up, you'll no longer be using Denon's amp; hence, no protection circuit.

Thanks, it is not a short as I have searched for it and could not find it.  Also if the system is cold I can go a lot longer before it trips.  I had the RC 70 set to large and sub set to LFE+Main with a 70 crossover.  I will try it at 120 as per your sugestion and see and may be increment down from there.  Is there a difference in setting the RC 70 to small or large  if I the sub set to lfe and main?

I have no experience with amps if I did get one where would volume be adjusted from?  I am asking because if the amp does it then this would be a pain if driving more than 2 speakers. 

I wouldn't suggest a sub crossover any higher than 90Hz as sound becomes localizable at that point and you don't want to be able to hear where the bass is coming from... it will destroy your soundstage.  If the speakers are set to large, they are still fed a full-range signal.  You end up with the fronts and the sub working to provide the sound up to the sub's crossover.  And that leaves the Denon working just as hard as not having a sub at all.  Small is the only thing any speaker should be set to.  See this link for a fuller but brief and well-worded explanation:

http://www.audioholics.com/techtips/setup/loudspeakers/bassmanagementbasics.php

All that an amp does is turn a signal-level signal into a speaker-level signal.  Period.  Volume is controlled from the Denon as ever, Audyssey still works, etc.  Find a Rotel 1070 and you'll be in a state of audio nirvana:

http://www.rotel.com/NA/products/ProductDetails.htm?Id=11

 I am experiencing similar symptoms with my Parasound A21 amp and Veritas 2.4i.  The left channel fuses blew, (located on the left side of the amp) after replacing them, the left channel came back to life.  I noticed the left side of the amp was getting very hot compared to the right side, and after a while the left channel started to clip.  Parasound suggested it could be the speakers and to switch them, left for right.  After doing so, I experienced the same problem on the right channel of the amp.  Evidently, there is a problem with one of the speakers units causing the overheating and clipping.

Have you found out the cause to your problem?  I've emailed Energy yesterday and am awaiting a response.  After reading some of the blogs here, I may be in for a long wait.