Marantz pm8006 vs Denon PMA-1700NE for combined home theatre and music room

Is your higher priority HT or 2-channel?  If the latter I think you’ll be fine running the center channel from the Denon.  For the stereo amp I’d recommend this Yamaha that’s at a higher level than the ones you listed and can be had at a steep discount here…
https://www.accessories4less.com/make-a-store/item/yamas1200sl-rb/yamaha-a-s1200-stereo-integrated-amplifier-silver/1.html

It has a HT bypass (they call it “Main In”) so when you hook the front L/R preouts from the Denon into the Main In on the Yammy the amp’s volume control is fixed so when playing HT the Denon controls the volume.  Conversely when you choose an input from a stereo source the Denon is completely out of the signal path and only the integrated amp is active.  I used this type of setup for years until I got a dedicated listening room and it really works great.  Hope this helps, and best of luck. 

@kota1 Sure, all else being equal bi-amping is nice but obviously costs more, and remember this is the OP’s second system so he may or may not feel the need to throw the works into this mixed-use system when he already has a dedicated 2-channel system for more serious listening. Between us he’s got two good options so really comes down to what his priorities and budget are.

Id like to have the option for playing the same music in this room to another but perhaps I’m over engineering it. I could just have a Wiim Pro connected to the Denon x3800H and then buy a cheap amp to serve the other room with another Wiim Pro connected to that.

Buy a second Wiim Pro and hook that one up to the Denon for the second zone.

Do you think the Fyne Audio speakers would benefit from a power amp in addition to the Denon or do you think the Denon would suffice for both movies and music?

NO!!!! Absolutely not. You do NOT want to use the Denon for music unless 2-channel is not important, and I think your Fyne speakers deserve better. The beauty of the setup I described above is that the Denon is COMPLETELY out of the signal path for stereo, which is what you want. The amps in the AVR are subpar and its preamp section is even worse and will kill your stereo sound quality. If you care about 2-channel in this system go with the setup I listed above.

@kota1 While I agree in principle, in practice I’ve found using the AVR to power the center works well.  To use the same amp across the front would entail buying a separate stereo preamp and a 3-channel amp that will cost A LOT more and add another box and set of interconnects.  To me it’s just not worth all that for the potential benefit, but the OP could certainly do that if he wishes. 

thanks! So should I connect the center speaker to the Yamaha as well as per @kota1 suggestion above?

No, the Yammy is just a stereo integrated so can only power the front L/R. 
 

So as per my original message "I was thinking of using the x3800h for my Center Speaker, Surrounds and 4 Height Speakers. I was then thinking of running the fronts via pre-out to another amplifier which has a main-in/HT-bypass to drive the fronts whilst watching movies. If connected via a main-in, it converts the stereo amplifier into a power amp only with the Denon x3800 having full control over volume etc..."  Should I leave the center to be driven by the Denon and keep it out of the signal path for music? If I do this, the F+L will be driven by the Yamaha and the center by the Denon for home theatre.  But all music sources (Wiim Pro, Turntable) will go direct into the Yamaha.

Bingo!  You nailed it and that’s exactly what I’d do if I was you FWIW.  It really is a wonderfully elegant and effective setup, and getting the AVR completely out of the signal path for stereo is HUGE.

@kota1 I think it really depends on the OP’s priorities. If he really wants to squeeze the nth degree of performance for HT I could see going with a 3-channel amp and stereo pre, but I think bi-amping is unnecessary and he can just use bi-wire speaker cables. The Yammy integrated I recommended is no slouch, and the Fyne speakers are a fairly easy load as well so high-power amps are unnecessary. Yes the center channel in HT is critical, but especially for movies the center is usually doing something very different from the L/R speakers, which is probably why having an AVR driving the center channel hasn’t bothered me very much and still find the presentation very enjoyable. I think having the same amp across the front is more important for something like surround music but not sure that’s a priority for the OP. Bottom line — I think the OP will be perfectly happy using a good stereo integrated with the Denon handling the center, but if he wants to up the HT performance higher than that for what to me are marginal gains, that’s totally up to him. There is functionally no added benefit to using a separate stereo pre versus an integrated, although if he spends more on a better stereo pre and 3-channel amp there could obviously be some additional sonic benefits to be had, but this will come at a price. It really just comes down to priorities and budget and how far he wants to go. To me, he’s already got a dedicated stereo system so there’s not as much of a need to go further with this system, but that’s up to whatever the OP wants. Just my $0.02 FWIW.