I have always used Quad electrostats as my main speakers. At first, they were the ESL57s, and these were a pretty nasty load for an amplifier, and did not take kindly to less than perfectly stable amplifiers. So I used them with Quad's own 303 power amplifier. More recently, my main speakers have been the modern and rather better 2805s. They are less efficient than the ELS57s, and when we also moved into a house with a rather larger living room, I replaced the 303 with a refurbished 2x140 watt Quad 606-2. The extra power was noticeable, particularly in more dynamic music. I am now wondering about getting even more power. The no-brainer option would be to get the Quad QMP monoblocks, for almost double the power. However, I am wondering if a more modern design like the Hypex NCore 400 would also work. Or is class D a non-starter with the stats?