The Q70 / Q70L with the 5.6 + AWD are the two most expensive and probably slowest selling models (as you know). However, I just did a quick search on CarMax. That is my #1 goto place to purchase a vehicle of any kind. I have bought 4 cars from 3 different locations and each time it was the most pleasant, least stressful experience. I also recently bought a Q60 3.0 coupe from my dealer and I still prefer CarMax hands down.
**** I am not associated with CarMax and I am not compensated in any way (although I should be for all the cars sold to my friends, etc)****
PROS:
1) They purchase / accept trades in larger numbers than most dealerships and they are picky about which cars they will actually keep and place on their lots for sale
2) They offer an extended warranty that beats ANY other company including Infinity with a very small deductible that is accepted even at Infiniti dealers
3) They have a 7 day return policy with no run around
CONS:
Their prices are always a little higher than other places but with an option for a 6 year warranty from date of purchase, you can rest easy as the miles add on.
Check this link. They will transfer any car from wherever it is to the store closest to you (for a fee).
https://www.carmax.com/cars/sedans/infiniti/q70