Hi, Glenn54! I have owned the Marantz DP-870 for many years (I think it was one of the first outboard decoders available). I have not used it for some time as I upgraded to a HT receiver a few years ago and took the unit out of the loop as it was not needed. I also bought the 950/770 in December of last year.

I have not heard the Acuras amps. But I can tell you that to my ears, the 950's perfpormance in DD runs rings around the trusty but aging Marantz. Just having the additional options for surround is great, and I have never heard DD like this before (not sure how much relative contributions to this conclusion are made by the 950 and the 770, but the resulta are superb). I have made no A-B tests, of course, and this is a subjective opinion. But I opted for the 950 and the 770 over some considerably more expensive gear, and think I made not only the right choice, but an outstanding choice.

Good luck!

Mike
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75" 4K HDR Sony XBR 75X95k mini-LED TV
Marantz AV7706 pre-pro
OPPO UDP 203 4K Ultra HD Blu-ray Player
Mirage HDT Speaker System (LCR [OM-5s for L&R and HDT-F for center], SR, SL, SBR, SBL [HDT-Rs])
Dual SVS PB12-Plus Subs
Outlaw Audio Model 7900 Power Amp w/Dual Emotiva CMX-2
AudioControl BijouTM THX� Equalizer
Rega RP1 Turntable
Dual Panamax M5300-PM Power Conditioners
Dual Monster Power HTS 2500 Power Conditioners
Dual Monster Power HDP 1800 Power Conditioners
Clearplay Blu-ray Player
Motorola VIP1200 HD cable receiver
Logitech Harmony Elite Remote