They sounded pretty impressive right out of the box, but have improved greatly over the last 3 weeks. It would be a huge understatement to say that I’m very impressed with their performance. The following are my observations on sound quality in no particular order: Large holographic soundstage, 3D imaging, completely black background, very neutral and highly resolving, tight defined bass, superb mid-range (vocals are awesome), rich tone, smooth and dynamic. Excellent performance from top to bottom, very musical and engaging (toe tapping goodness!) I’ve been in this hobby for approx. 30 years, and at no time have I come across the price / performance value that NuPrime offers, it really is unbelievable. These amps are the real deal, and I will be keeping them.