Looking for an integrated amp around 4000 to 5000.

Hello - wow you got some kind and sincere responses and some odd recommendations but that’s to be expected. Folks on this site for the most part are kind and want to help you. 
Ok let me try to help. 
First things first. Over the years I’ve owned many different speakers and many different kinds. Bookshelf’s, panels. Single driver, Electrostatics, full size the works. I owned these Ascendo C8’s for years and loved them. I bought them right after owning a pair of Wilson Sofia 2 and they are much better IMO. That rear firing ribbon tweeter is odd and I never used it but some people like it I guess. 

So the challenge with these is similar to the pair of Martin Logan Summits I owned. To get the bass driver to match the panels speed and blend properly. 
Your speakers have an internal base driver that honestly I worked hard to find a good match. I first tried tubes CJ, ARC, PL, etc.

Then SS. Pass, Krell, Mac, Ayre. 
Here is the thing. They need / demand driver control / high damping factor. Give them the best driver control and juice you can afford. 
I now use Magico S5 MKII and these respond best with Soulution and Vitus IMO. Both grab and hold the drivers so we’ll. Of course there are other great matches. 
Your speakers have some warmth to them so I recommend SS for sure. 

The 88db / 6ohm is not what to look at really. The better driver grip the more your internal driver will march that nice mid and tweeter set up. Focus on the amps grip. Trust me. Get the highest damping factor you can afford. Watts help but damping factor will lead you to the promise land. 

Forget about brands or recommendations. Get a high quality SS amp with the best driver control / damping factor and you will thank me. I tried a dozen amps to get these right and difference was night and day. 
What is your budget. 
For example for my Magico S5 MKII I was using Pass Labs XA160.8 with damping factor of 200. Pure class a, warm great amps and I was happy. My Magico’s are no where close to relying on damping factor specs compared to the C8 but as a rule Magico’s really want their drivers held petty tight. My Soulution 530 has a damping factor of 10,000 vs the Pass Labs 200. Nelson keeps them sort of loose and that helps give them that warm, round and inviting sound.

With my Soulution I unplugged my pass amps and plugged in my 530 and let it warm up for a couple hours playing Roon radio and did some yard work and came Back in and had a listen and was blown away. The Pass Labs class a monobocks were gone in less then a week. 
The 530 is a very expansive amp but still for Ascendo C8 you need to get the highest damping factor you can afford. 
Now I’m not saying this is the only spec that matters. Get the best quality SS amp with the highest damping factor you can afford. Watts mean nothing really but can help. My Soulution is 130 watts and blew away a 450 watt amp so please do your home work. 
Maybe some folks on here know of a good high damping factor amp that sounds great in your price range. 
What is your budget? 
Will you consider a used amp? 

I personally owned these speakers. I tried close to a dozen amps on them. Damping factor on these specific speakers matter. The inside bass driver is slower then the mid and you can hear it with a first rate source unless you get them dialed in just right. That is my experience. Other may differ or not agree. I’m just trying to help the guy. 
Yes damping factor for the most part is not super important but it certainly is when you have a speaker that needs it and badly. 
I wasn’t using cheap amps either.

The best I settled before Soulution was ARC 250 SE which I thought was great until I heard the Soulution.

I am not recommending a Soulution amp. I use a Stage III Kraken power cable on it that cost much more then the Ascendo’s do but trust me get a good amp that has a high damping factor. 
Now if someone else chimes in that owned these speakers and they worked hard like me trying all kinds of different amps to get most out of them then great listen to them but people that have not owned them and don’t know these unique German speakers just ignore them. 
djones51 
I didn’t even read your link. I owned them and worked hard to mate them. Some article / white paper will never compare to actually owning and then spending tens of thousands to properly drive them. 
I actually am trying to help the guy rather be a contrarian. I have not posted on here in a long time but thought the op could benefit from my personal experience. If not no problem but people should actually try help when they can.