No, that won’t work IMO. Chasing a deal that might solve only part of your problem isn’t really much of a deal. Replacing the preamp section of the 6011 is just as important as replacing the amp (preamps matter!!!), which is why a stereo integrated is such a great solution as you’re removing the Marantz completely from the signal path for 2-channel with just one additional box — plus it’s more economical than buying separates.
For example, you could get an Ayre AX-7e here now for about $1500 that’d take your 705s to new heights. Another great option would be a used Hegel H160 that can also be had for about the same price, and either would be a huge step up from your AVR. Frankly, you could even buy a new NuPrime IDA-8 for $1100 at Audio Advisor, who I believe has a good return policy, and give it a try and just return it if it doesn’t blow you away. It’s a multiple award-winning integrated that also has a pretty good DAC you might also appreciate, and I’m confident the IDA-8 would greatly improve your 2-channel performance (read reviews at Absolute Sound, Soundstage, etc.).
Anyway, if you take anything from this please let it be that you need to get the Marantz COMPLETELY out of your 2-channel signal path to realize truly good stereo performance. Just my $0.02 FWIW.
For example, you could get an Ayre AX-7e here now for about $1500 that’d take your 705s to new heights. Another great option would be a used Hegel H160 that can also be had for about the same price, and either would be a huge step up from your AVR. Frankly, you could even buy a new NuPrime IDA-8 for $1100 at Audio Advisor, who I believe has a good return policy, and give it a try and just return it if it doesn’t blow you away. It’s a multiple award-winning integrated that also has a pretty good DAC you might also appreciate, and I’m confident the IDA-8 would greatly improve your 2-channel performance (read reviews at Absolute Sound, Soundstage, etc.).
Anyway, if you take anything from this please let it be that you need to get the Marantz COMPLETELY out of your 2-channel signal path to realize truly good stereo performance. Just my $0.02 FWIW.