I was curious how the pre-outs on the Marantz 7011 measured. Unfortunately there is no amp disconnect feature for alle channels (only the hack for the mains). Hope someone can shed more light to use, even though the receiver is a couple of years old now. My five channel amp have a sensitivity input of 1.5v.
The measurements of the following should give you a good idea of what you can expect from the SR7011
Audioholics.com review:
SR8012
ASR reviews:
SR6014
AV7705
ASR reviewed the SR6014. The SR7011 should performed about the same, likely a few dB worse, like the AV7705 did, but imo there shouldn't result in any audible difference. So just relax and enjoy, especially if your 5 channel amp only needs 1.5 V for rated output, unless you listen loud, sit far away, and/or have low sensitivity speakers.
What did the online spl calculator tell you about your power needs? That should always be the first and most important step for anyone who is concerned about sound quality degradation due to pre-amp and/or power amp output limits. If you only need preamp output up to 0.5V, power amp output 10 W, then any AVR will do, but if you need preamp output up to 4 V, and power output 300 W/500 W 8/4 Ohm, then you would have to choose carefully.
You do have the option to run the front left and front right levels in "pre-amp mode" (practically speaking), using the amp assign feature. Whether it would make any audible improvements or not, it's free and easy to use that feature, so why not?