I've known that the CP-8 used a Denon engine all along. When I was a dealer, it was publicized to all of us (bragging that it works). I sold two of those 200 prepro's. I factually told both of my customers it was a Denon Engine. To me at least, that was a selling point. Most "highend" prepro's and HDMI are incredibly buggy. I'll change that text to ALL highend prepro's I have come across are buggy. the prepro section works BETTER (and certainly less buggy) with Denon/Marantz, Yamaha, Pioneer, or Onkyo. But some Japanese prepro IMHO, don't sound good to my ear. Onkyo comes to mind. Small companies go out of business like B&K, ATI, Theta, etc because designing the engine is incredibly expensive and STILL very buggy. When they finish, the HDMI creates them heartache (and returns). B&K's REF 70 got a 20% return ratio company wide (source: Ed and co-owner of B&K). I sold about 50 of those.
If memory serves me, Simaudio WAS distributed in JAPAN by this company called “Denon”. Hence, I fully expect Denon sold them the boards. If they did and they told you that they didn't, don't be surprised. Simaudio isn't dumb Marshall. It's damn easy to see that it is a Denon ENGINE. Good work Sherlock Marshall. Currently Simaudo is distributed in Japan by "Dynaudio". Yea. The speaker company. Guess what.. Simaudio distributed Dynaudio in the late 90's. That sounds weird but it often happens like that all the time.
But the analog section in the CP-8 was dramatically different. Is it worth $18K? Not in to my ear but I am missing only lousy zero in my net worth. Does it sound better? HELL YES! Was it worth it to my customers? Yep! They had that extra zero next to their net-worth. Realize this Marshall. Some people make a LOT more money than you and I and they don't care what thy spend. This may seem surprising to you. But people buying $18K prepro's usually are MULTI millionaires. Don't assume they care.
So the true question is how much different is the analog section. I'm not in the camp that thinks "all amps, preamps, DAC's sound the same". SQ differs in the analog section, reducing jitter in the digital section, and room correction differences. IMHO, the CP-8 accomplished this goal. It was an amazing sounding prepro for someone who wants the very best.
I was told it was very similar to a Simaudio P-7’s (if memory serves me) times all channels minus the volume control advancements. Simaudio also added a deferentially balanced design (not fake balance connectors), beefy power supply, changed the signal path capacitors, used discrete operational amplifiers versus 20 cent semiconductors etc. The end result is the CP-8 DID "smoke" the Denon receiver (which I also sell).
Most of the boards are nothing more than software (room correction and DSP modes) on the DSP. So they could of used an Onkyo board. But they had an ongoing relationship with Denon.
But $18K??? Not for me personally. But do realize that they had large promo’s on the prepro’s when you bought the amp. So $18K is a fictitious retail unless you only bought the prepro. As most vendors know, the profit margin is in the amps. They build prepros to sell amps. Ask anybody who makes these products. I sold the two Sim prepro's as a stack and the customer saved a lot by doing so. Marantz does the same thing with their new 8801. Buy both and the dealer gets a better deal and he passes it on.
Selling DSP boards is nothing new. ATI sold Simaudio the prevous board. They also sold BelCanto theirs. Marshall. There is am article for ya. ATI was 1/3 the price of the Bel Canto. The prevous Simaudio was a EAD. Again, so what they had a different analog section. While we are at it, the former Parasound prepro was the same engine as the Halcro (and 5 others) that was designed in Finland. As you see, it is common place for many people in this industry. And yes, I told my customers that the Lexicon RT-10 DVD player was a Marantz 8400. A RT-20 was a Marantz 9200. Jeremy Frost of Lexicon confirmed it. People still bought them (3X the price and 1/3 the warranty). They wanted the stacked look. They had the money is just didn't care. No. Lexicon didn't advertise that their amps were really Bryston and later Crown, and later ATI. Nor did they advertise that their DVD player was a Marantz and now an Oppo.
If you want another hour of other examples, email me. I own Sound Video here in MN. This time don't think that 5 year old information is "new". I'll give you the scoop before the following decade is finished.
Steve