Marantz sr 8015 in pre pro mode or Marantz av 7706 processor

[dhp]

I'm looking to upgrade my system . I'm trying to choose which of the above options would give the best sound quality .

I live in a Flat so don't need masses of power . I want clarity, detail and an immersive experience. Music is also important. I've not found a dealer who has both in stock so I can do a comparison demo.

I'm currently using an Onkyo TX RZ 840 .