I came across the 1604 due to a mix of features:
1. Little height (better wife acceptance factor and better utilisation of available furniture)
2. 7 channels with assignable bi-amping
3. Room correction
4. Airplay support
... and all the other modern goodies this receiver would give me over my 12 years old Onkyo unit.
Now the slim form factor would be reason alone for me to get the unit, to use it for the following scenario:
2xKef Q500 front speakers bi-amp driven (please don't ask me why the WAF isn't an issue with standing speakers)
2xKef Q100 surround speakers
... and that's that.
May sound strange but I come from a stupid Bose Acoustimass 5.1 system that is just a boombox sourcing its bass signal mixed from the 5 channels that feed it with 5 cheap miniature broadband drivers dangling from it. And I'm sick of the consequences: Reasonably potent but very boomy bass, in movies constantly too quiet voices (I don't fancy the idea of a dedicated center speaker anyway), no discernible surround effects at all. Stereo music is even more hopeless and that is where I'd like to see the biggest gains. Hence also no interest to spend considerable money on a single subwoofer, but rather have a pair of standing speakers.
The room is midsize and pretty much catastrophic both in geometry and reflectivity and I have no intention to do physical tuning, so that is where I hope Audyssey will come in. As far as I understand the version implemented in the NR1604 is pretty basic - will it apply the filtering in (bi-amped) stereo mode at all? Will it then brush up the Kefs' allegedly somehow sloppy bass response? Does it do a good job at phantom mode for the center and the subwoofer? The manual states there are options that can be set this way, but Marantz isn't specifically promoting the possibility to go without a subwoofer as I've seen somewhere else (Yamaha I guess).
So I'm really aiming for worthwhile stereo at reasonable volume levels (Kefs are 88dB) with a nice 3D soundstage (this is where the Uni-Q drivers should come in), sometimes from Airplay when I'm too lazy for dragging the CD out or when throwing a party. Surround sound would only have to be an add-on for a movie once a week or two. Do you think the setup will work out like that?
If money allows I might go with similarly sized Kef R series instead of the Qs but I admit that this would rather be an extra treat for the ego than a necessity.