It isn't about watts, it is about your Marantz pre/processor being your two channel pre. As nice as the unit is (I'm sure) for HT, it is not a dedicated 2 channel pre for music. That is your problem. There is a still a lot of processing hardware it is 'shared with'.
I've been there/done that. And not until I separated my AVR (in my case) from my/a seperate two channel rig for music only, did I hear a significant increase in 2 channel sound quality. In my case, I did that with a dedicated 2 channel preamp that has HT bypass! via the AVR 'front' preouts, and then connected to a separate 2 channel amp. My music sound quality was greatly increased by getting the AVR/processor out of the signal path for 2 channel. And with the bypass, I simply switch that on when using my AVR for HT. The center and surrounds are then driven by the AVR. All of my 2 channel equipment is connected to the dedicated 2 channel preamp (turntable, tape deck, DAC, etc.), so the processor is not in the signal path at all.
Issue I see is you have a fairly expensive dedicated 3 channel amp and HT processor/pre. I'm not sure adding the Krell to this makes a lot of sense quite honestly as I don't see it has an HT bypass option.
What you might want to consider is selling both the Marantz and Emotiva, and getting a high end AVR with front preouts just for HT where the center/surround sound quality is not as critical as 2 channel music. Then, as was suggested, get an integrated 2 channel amp....*but with HT bypass*. in that way, your front channel will simply be powered by the integrated in 2 channel, but the front, center, and surrounds processed by the AVR/processor in HT bypass mode.
