Used 5ch Amp (Classe, Krell, Rotel)

If you don't have space limitations, consider a 2 channel amp or monoblocks for your 2 front speakers and keep the Rotel for surround duties. You'll spend less and should be able to get better sound. 

There are no really good 5 channel amps. There are no really good 5 channel anything. 5 channel is Home Theater. HT is a wasteland.

Already you have noticed. No multi-channel anything sounds as good as 2 channel. You know this from listening. All you need to do now is take the next logical step and transition off the whole HT train.

Start like big_greg suggests with stereo components. From here on out simply upgrade only the stereo elements of your system. Let the surround crap go. If you feel the need, upgrade to a Swarm type distributed bass array that will improve both movies and music. But let the HT dreck go. You know you want to. Your ears are already telling you this. Don't listen to the marketing. Listen to your ears.  

Yup, @big_greg and @millercarbon are giving you sage advice.  If stereo is important to you, then focus your money there and don't waste big bucks on powering your surrounds.  The other issue is the Arcam -- its preamp section is sucking the life out of your 2-channel performance, probably even more than the amp.  

So two choices -- get a good stereo integrated amp, or get a separate stereo amp and preamp.  Either will work fine, but the integrated obviously saves you space and a pair of interconnects and will likely be a better value too.  A HT bypass function, while not necessary, is nice to have in a hybrid system like this. 

Now, all you do is run the front L/R pre outs from the Arcam to the HT bypass input on the integrated (or any unused line-level input).  When you want to do HT just choose this input, and when stereo choose the appropriate input on the stereo pre/integrated.  Obviously your DAC or whatever stereo music source is now hooked to the stereo pre/integrated instead of the Arcam. 

The real beauty of this setup, other than only having to flip one switch to toggle between HT and stereo, is that in stereo mode the Arcam is now completely out of the system and has no affect on the sound.  I suspect you'll hear a not small improvement in what you get from your Dynes in 2-channel.  Anyway, best of luck. 

BTW, here's a really nice integrated I'd bet would sound fantastic with your speakers.  Not sure what your price range is. 

http://www.audioasylumtrader.com/ca/listing/Integrated-Amplifier-SS/Hegel/H360-Integrated-Amplifier/...

FWIW...