Adding 5-channel amps to AV Receivers


I'm currently shopping for a used 5-channel amp to use with my Denon x3400h receiver with a 5.1.2 Atmos setup, speakers are the older SVS SCS1/SB1 which still do great.  This setup is 100% movies/video games, music is for the 2-channel setup upstairs (Levinson, Revel, PS Audio).  The home theater is never going to get the budget that the music system gets, but its still a lot of fun and Dolby Atmos is really cool with down-firing ceiling mounted speakers.

My question - It seems like adding a separate 5-channel amp to pretty much any AVR would be a very standard setup for anything above a low-end home theater setup, but I rarely see it discussed.  IMO its asking a lot of a sub-$1k receiver to handle all the processing and 7 channels of amplification with its single power supply.  When you can buy a used Rotel, Parasound, etc 5-channel amp for less than $500 and let the AVR be the processor, this should be a no-brainer right?  Pulling out at least 5 channels to a real amp should have all kinds of obvious benefits.  Even if the speakers are not full-size, reasonably efficient, and there's no clear need for more power, this should still produce much better sound.

It seems like an obvious move but its hard to find any discussion of it, usually the conversation goes from budget AVR to high-end AVR to separates.  Am I missing something here?
jimmywho
Most receivers that are spec'd for say 120 watts per channel, will only actually do that with one or two channels driven.  Usually the specs for multi-channel amps are for all channels driven.  Adding an external amp should give you more headroom if nothing else and if it's a decent amp, it should sound better than whatever they were able to stuff into the AVR box.
Personally I wouldn’t do a 5-channel amp unless I was big into high-quality surround music.  Short of that, I’d rather do a better 3-channel amp for the L/R/C and let the receiver power the rears.  There’s a McCormack DNA HT3 available now for $800 (List $2300) that I’d jump on if you want a big upgrade to your HT amplification. 

That said, if it were me I’d upgrade to something like a used Anthem MRX 520.  Why?  Well, as audiophiles we know the preamp is as or even more important to the ultimate sound quality of a system as the amp.  So bu upgrading the amp you’ll likely get some improvement, but you’re still stuck with the preamp section of the Denon.  By going to an MRX 520 you’d not only get better quality amplification but also a much better preamp and arguably better surround processing as a further bonus.  Put all those together and the resulting increase in overall sound quality will likely far eclipse just inserting an amp in with the Denon.  Used MRX 520s do pop up in the $800 range from time to time, which is only a little more than you were planning on spending on just an amp.  

Anyway, two other options to ponder.  Best of luck. 
Good replies fellas I appreciate it!

Soix - Great point on the Anthem (and spot on with pre-amp importance), that one was not on my radar, but you're right, for $800 or so used that's really compelling.  I had not given much thought to higher end receivers, but if I see one come up for sale I'm going to buy it.

Also good points on the 3-channel amp instead of the 5-channel.  For whatever reason, quality 3-channel amps seem to be either more expensive or less available than 5-channels, and I thought I could run the five SVS speakers with the same amp, and run the other 2 with the receiver.

I did snag a B&K AV5000 5-channel amp on ebay today for only $200, that's supposedly a pretty decent amp, so I'll do the experiment with the Denon and post back.  I can sell both the B&K and Denon if the Anthem beats my budget separates combo, which it probably will after reading about it for a few minutes.

Happy Holidays!  
My suggestion is get an inexpensive 5 channel Marantz from Accessories4Less and then see if you need anything more.

Best,
E
I agree with the OP, this should be a no brainer .  I added a Parasound 5 channel amp years ago to a Pioneer AVR and it was an obvious upgrade sonically.