You don't need to wait for Marantz, the SR8015's amp assign feature works the same way as the SR6015, and AVR-X6700H, you can only assign the front L and R to pre out, aside from the default settings that depends on your floor and height layouts selected.
It is on page 250 or the owner's manual:
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It is rare to see Canadians price better than US price. In this case, it is C$1899 vs US1999, converted to US$, price in Canada for the 6700 would be about US$1370, that's $629 cheaper!! The last time I saw that happens was a few years ago when we can buy the SR7012 and 7013 at lower price here in Canada than in the US.
Unless you can get the SR8015 down to around $2,500, I would find it tough to justify paying so much more for the SR8015. I know what people says on forums, but I am 100% sure in a blind test, all those claims of the so called music, or warm Marantz sound will disappear completely. I have owned and still own enough Marantz products, in addition to analyzing information in some of their service manuals to know that those D+M equivalent models are virtually identical in terms of the parts and circuitry of the audio signal path. The SR8015 does have a better build, as you will get some copper plates, and a toroidal transformer but none of those matters in terms of specs and measurements based on bench test results on both Audioholics and Audiosciencereview.com. In fact, in preamp mode, the X6700H still edge out the 8015, though the 8015 has improved by miles, versus any of the earlier models measured on ASR.
So since you are in Canada, it should be an easy decision based on the super low price of C$1,899, brand new from Denon, presumably with full warranty. At that price, you can use it for a year or two, and then trade it in for the near flagship upcoming 20124/25 models and likely can get at least the same value for the trade-in credit.