Berlin Hbf to Brussels Midi via night train

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I'm interested in traveling from Berlin Hbf to Brussels Midi/South via the night train (00:12 - 8:32) in late August or early September.  I've checked with Bahn.de and am unable to find ticket options or even purchase.   

What's the approximate price?  Also, what's the best way to purchase? 

Thanks and appreciate the input. 

00:12 - 8:32 it is not direct train, but connection with change in Cologne. And apparently DB doesn't sell discounted ticket for such connection. So if you intend to use it, then you will have either to purchase two separate tickets. One will be from Berlin to Cologne (for CNL 456 train), it starts from 48 EUR (seats), 64 EUR (couchette) or from 104 EUR (sleeper), while the other one for Cologne-Brussels Thalys/ICE trains, those start from 19 EUR. You won't have any problems buying such tickets from DB website.
Also possible option will be to purchase international discounted ticket Berlin-Eindhoven for the same CNL 456, which after Cologne continues to Amsterdam via Eindhoven. Berlin-Eindhoven with Europa-Spezial Niederlande offer will cost you 43 EUR for seat, 59 EUR - 6 berth couchette or from 99 EUR for the sleeper. Then just continue from Eindhoven to Brussels, full standard ticket cost 29 EUR.
Also might be useful to read this topic - http://europetrainsguide.com/forum/index.php/topic,329.0.html

Thanks for your help.

With the CNL 456 arriving the Koln Hbf at 06:14, will that be sufficient time to make the 06:44 train to Brussels?

With the CNL 456 arriving the Koln Hbf at 06:14, will that be sufficient time to make the 06:44 train to Brussels?

Yes, half an hour it's plenty of time. You even will have a chance to go see the Dome
Even if 456 for some force majeure railway reasons will be late and you miss your 6:44, then DB should allow you to use next train to Brussels with no problem.