Hi my friend! Don't by a used Class D amp. They are all made before the newest and best generation of Class D amps were developed. You can buy new for under $1400. If you catch a "sale" price, even less. The big deal is that Class D amps have finally come to fulfill the promise of the concept. The new generation are really a lot more like AM radio transmitters than a conventional audio amps. Once some fellows who understood UHF and radar gear turned their attention to audio, amazing things began to happen. Purifi Audio (Denmark) now produces an output module that is wining acclaim in other people's products. Starke Sound (USA) offers a complete, ready to go, four channel amp (perfect for two way speakers used with electronic crossovers) that is not tiny and cute, no chrome, no sculptured casework, uses a conventional power supply, is big and heavy, and sings like a bird. To me, the Purifi and the Starke sound nearly identical, and as good or better than anything I ever heard. If anything, the Starke may be very slightly sweeter on the top end. Very.
To paraphrase Meredith Wilson, either amp will, "Grab your woofers, grab your tweeters, in the arms of a dominating irresistible grip and deliver the clearest, cleanest music you have heard in your home." I admit that's a pretty outrageous paraphrase, but it gets the point across, without resorting to "techie" talk. It is the music we want to hear, isn't it?
What amazes me the most is how whatever speaker I drive with either amp, they sound very similar. I have about 12 sets of speakers in the house to play with (and a very tolerant wife), DIY and commercial (Shahanian, Wharfdale, Golden Ear, Spika, a couple more, bookshelfs & floorstanders, There is not a wide difference in "flavor" between them. The amps CONTROL the speaker. These amps are switching tiny bits of 100+ volt "juice" into the voice coils. No speaker can fail to respond to that! And the amps, through the use of large amounts of feedback (the Purifi module has only 13 db of gain), can detect and correct any errors the speaker makes almost instantaneously. The result is extremely low noise, extremely low distortion sound from whatever speakers you are using. Of course, quality matters; but these new Class D designs will get the most from any speaker connected to them. Read the reviews. Best of all, the Starke AD4.320 (four channels, bridgeable at the flip of a switch, phono & balanced inputs, sells for under $1400, brand new, delivered to your home. It's worth a try. The NAD M33 is about $5000.Easy choice? I am interested in the best sound for the money. Ah well, that’s all for now. Happy Listening.