Hi ss2nv, another big congrats to your setup, you have a fine selection of excellent gear meant to please eyes and ears for an extended period of time during the coming years, the least to say.
Also appreciate the good quality photos you have shared, meantime it would be also nice to see the rear side of the room provided you have surrounds or even rear surround speakers.
Furthermore, if I may, I'd like to give you some more "tips & hints" on how to make improvements in SQ (sound quality) with a bit more effort.
1. As others have already noted your front wall seems to be too much "empty" and that emptiness may cause a lot of unwanted reflections especially in the mid to high frequencies degrading sound imaging and dialog intelligibility. Wall treatments may/should be a good solution, but since as I see this is a living room a bit more furniture may also do the trick. Sometimes bookshelves (with a lot of books) will do just fine for taming such phenomena. Please take a visit to my setup (link in my sig) to see how my front stage looks like.
2. About center speaker: proper setup is mainly responsible for dialog intelligibility. You may try to find a way to tilt it with some clever supporters to make it face seated ear hight and you may also try to put a small table cloth under it to tame reflections (in the mid to high frequency range) in order to avoid an effect called 'smearing".
3. Coffee table: although I know very well that a coffee table in a living room is a must, but again to tame reflections off that hard surface another table cloth is recommended. You may consult WAF and give her a free hand here. She will appreciate your thoughtfullness. Guaranteed!!
4. Subwoofer placement: if it were me I would put the sub between the cabinet and the right side tower. Placing it into a corner (as seen on your photo) may result in something called "boominess" as a result of "corner gain", but a placement out of the corner will most probably help tackle this issue so that you can get smooth, deep and even bass.
5. Although you didn't mention, hopefully you have done the auto setup with Audyssey MultEQ XT available on your Marantz. When done just set all your speakers to "Small", choose a crossover frequency of 80 Hz for all speakers, open up a cold beer and enjoy!
6. Here's a song from a Danish group you may play to test your system will all possible frequencies from deep bass to mind blowing highs: Bliss: Song for Olabi
Come back please.