Replacement for Marantz AV8801: another prepro or receiver?

I will keep using the Parasound A21+ for the 801s -- it's a fantastic combination that sounds great, whether it's playing softly or rattling the dishes  The Parasound made an amazing difference over my 30 year old Nakamichi PA7 amp, keeping everything in the music mix crystal-clear even at high volumes without any congestion.  My lovely wife no longer complains when it's up loud.  But this is something I don't want to lose by going to a lesser preamp in the preprocessor. 

This mix is 80/20 movies/music with music streamed mostly from AmazonHD or my ripped CD collection from FLAC.  I don't play records very often (mine are all very old and scratchy), but still need a phono section.  But music is on quite a bit while I'm doing other things in the house, and Alexa/HEOS with AmazonHD music would be a welcome improvement, especially if everything can be turned on with a voice command rather than using 3 remotes (the Nak has no 12V trigger). I know both Marantz and Denon do this well.  And I've seen comments online that the analog section in these AVRs is really pretty good. 

So, after a whole lot of forum perusing, I'm now tilting towards the Denon AVR-X6700H (140wpc x 11) -- the price is right and it wold be great if I could use it to biamp the HTM71S2 center (not clear if that's possible but not a deal-killer as the center is not really used for music).  That leaves 9 channels for the surrounds -- 2 sides, 2 rears, plus maybe 4 smaller speakers in the ceiling for Atmos, none of which should tax 140wpc (I know it's less if all channels are driven). There is also the higher-end X8500H or the ridiculously priced A110 but those are both 2017 or maybe 2018 designs (8K support was added to the A110 and). I think I've learned that lesson -- get the latest prepro possible and only expect it to last 6 years. Bummer, but it is what it is. 

And I've seen comments online that the analog section in these AVRs is really pretty good.

Well, pretty sure you didn’t read those comments here.  IMO you have a good amp and speakers, and it’d be a shame to hobble them for 2-channel listening with the crappy preamp section of an AVR (unless you really don’t listen critically).  I think taking advantage of an AVR for the processing and amps for the other channels makes a lot of sense, but I’d recommend investing in a good stereo preamp with a HT bypass to handle stereo listening as it’ll greatly your improve performance there.  Preamps matter — A LOT!  Just my $0.02, and best of luck. 

It doesn’t appear as though the OP gave Anthem much consideration.  The Room Correction is definitely a plus, particularly 2 channel listening.  Why would you go back to Marantz after the bad experience you had?  Even if their products were more reliable Anthem is superior quality.  I haven’t bought any Denon gear for a while but since they merged with Marantz I have heard that it’s the same stuff, different logo

I've been using the Marantz 8801 as a preamp and enjoyed listening to it with two channel music or 3 channel video for movies. While a dedicated pre-amp might get me a little closer to nirvana, since I don't have a dedicated listening room (the kitchen is nearby) and we spend much more time watching movies and TV than critically listening to music, squeezing the last ounce out of 2-channel listening probably wouldn't be cost-effective. That said, I still have the Nakamichi CA-7A preamp from the 80s, so it'll be fun to swap that in to see how it sounds.  Given the age and the fact that it's never been serviced, I'll have to see.

I've seen comments that the preamp section in the top-of-the-line or near-top Denons outperform my 6-year old 8801 although the lesser power supplies cause me to question that. Still, I do like the way the 8801 sounds on 2-channel music so I hope that's true. I also believe the top-of-the-line units can disconnect the amps and only function as a pre-amp.
Regarding Anthem, teh room correction does look terrific, especially since I wouldn't have to run a super-long mic cable to my equipment cabinet.  However, my dealer doesn't carry it and other than custom install shops, there are no dealers nearby (according to the website).  It also looks like they're in the midst of a changeover to new products, releasing this month which have a lot of "coming soon" and no longer list PlayFI. HEOS is something that really interests me for playing lossless music like Amazon Music HD over the interwebs.  Integra has PlayFi, so that might be worth a look -- just haven't heard much about that brand.

Anthem also doesn't have an analog component video input (yes, I still have a VCR and have recently been using the Marantz to convert, upscale, de-interlace and capture family video using a cheap HDMI capture device -- still a work in progress).

Anyway, thanks...

we spend much more time watching movies and TV than critically listening to music

Under these circumstances I’d just get a good AVR and call it a day.  I don’t think it’s worth the added hassle/expense of buying a prepro and separate amplification.  If you’d appreciate a little more transparency, detail, and reliability I’d go with a Yamaha RX-A2080 or 3080, but if you like the warmer, fuller Marantz sound just stick with one of their AVRs.  And you should definitely try the Nak preamp — could be very interesting.