High end Class D amps?

bluorion:" @noble100 Thank you for that information---so would it make sense to add a class D power amp to a class AB integrated with a pre-out to get more power if needed? I realize that may sound weird but if you have a 100wpc integrated, for example, and need more power for a pair of low efficiency speakers, adding a 200+ wpc class D would be ok?"

Hello bluorion,

     Yes, I believe that would work, however, it's not ideal and I think there are a few details you need to consider:

1. It's important to impedance match, which means ensuring the input impedance on the class D amp or amps you're using are at least 10x more than the output impedance of your integrated amp's pre-outs.  
2.  It's very important that you really love, not like, I said love the sound of the integrated amp's pre-out section because the majority of, if not virtually all, good quality class D amps are neutral in the extreme. 
     Good quality class D amps, in general, are very low distortion and very low noise system components that you'll definitely perceive as not adding or subtracting virtually anything from the inputted signal or signals.  The good ones function very much like the audio ideal of 'a straight wire with gain'.
     I know you stated you wanted to use the pre-out section of an integrated amp, in effect using the preamp section of the integrated amp as your preamp.  But I don't recall you stating why you want to do this or which brand and model you own or plan to use.  Can you please clarify?

Tim

Finally I own a pair of Nuprime Ref.20 Class D with some modifications (silver wiring, Duelund Bybass caps, WBT Silver binding posts...) They are amazing. I feel no need to go back to Class A - but to be honest before I met them by chance never thought about class D. I shared the same prejudice about Class D. Lacking Detail, thin shrill Highs... The Nuprimes Evos are even better. Hopefully I get the chance to grab a pair in the near future. The only non Class D Amps that would be on my wish list are Boulders. But - to be honest are financially out of range and wouldn't work with my Plixir power conditioner. 
I own a full MSB Signature V frontend (CD and Dac), modified Pioneer/TAD S1 Speakers, cabling is Neotech 1001.
Sorry if my english isn't perfect - I live in Germany 

Based on  boomerbillone's comments on the Starke AD4.320 in this thread, and the very aggressive Black Friday pricing of $839, I bought the amplifier and it was delivered Wednesday.  I let the Starke AD4.320's burn in for about 20 hours and spent a few hours tonight comparing it to the PS Audio M700's which are Class D monoblocks costing $3000 and a Stereophile A rated choice. The M700's are rated at 700 watts into 4 ohms vs the AD4.320's 430 watts bridged into 4 ohms. I listened on the Magnepan 3.7's and the amps were driven directly by a SMSL SU-9 DAC streaming over bluetooth and level matched to pink noise at 75 dB.  I fried my Roon Core a couple of days ago and couldn't stream via USB. Bottom line is I really liked the AD4.320's. The have a very dynamic, rich sound while still being very detailed and quite a large and deep sound stage. Bass is tight and impactful without exaggeration. Midrange is warmer than the M700's which tend towards a little dryness. Highs are bright and detailed without any harshness. The AD4.320's struck me as bringing some of that subtle magic that a good set of tubes in my Freya Preamp can offer over its solid state modes. I usually found the AD4.320's to be more engaging and dynamic than the M700's. I generally have preferred the M700's to my Parasound A21 class AB amp with the Maggies except in the mid-range vocals and I think the Starkes bring some of that better midrange while having great bass and dynamics. For the Black Friday sale price of $839 I have no qualms about recommending the AD4.320's and to my ears they punch way above that price. Very fun to listen to.  I would love to hear the opinion of some of the more experienced ears on here that have actually heard the amp rather than just get flamed by all the Class D haters.

@noble100 Hi Tim---thanks for the info. I don't consider myself a new audiophile per se, but in the past, I didn't really pay much attention to specs like I do now. I was a young 20-something back then and just bought what sounded good. As I've gotten older, I've become more interested in what matches better with what and I'm trying to learn from all you guys. So now I have a Luxman 505UXii integrated with a pair of Dynaudio S40s as well as  pair of Tekton Lore References. I alternate b/w the Dyns and the Lores depending on my mood and musical tastes. I love the Luxman but I at times I wish it had some more punch or something. I caught a video on YT recently that had a new Luxman connected to a Pass amp (I think)---I can't seem to find it now. Anyway, it got me thinking about higher output class Ds (like 200+ wpc) and wondered how that would go. I really appreciate everyone's input and suggestions. 

The Japanese company Spec design very well regarded Class D amps that are apparently very valve-like in tone, though they are not the mega-watt things that a lot of people seem to use Class D for.

I have 300W Class D amps in each of my semi-active speakers and they work brilliantly at driving bass.  But the passive end of the speakers I prefer driving with Class A.. It is the perfect combination.