What are the best GaN Amplifiers available today?

Aavik uses the Pascal modules. I currently have Hypex based Ncore NC400 monos with a BAT VK-40 preamp, I would like to upgrade to either the new Hypex Nilai 500 or the Aavik I-280. Very difficult to find comparisons. 

@blisshifi No problems, the Pascal modules (UMAC) don't use GaN technology, one of their features that makes them different to Hypex, Pufiri, IcePower and the rest of the classD designs is that they use a sinusoidal waveform instead of the more widely used triangular waveform to produce the PWM so theoretically the output filter design is easier and should produce less RF noise. That's the theory.

You say they sound great, I have never heard any Aavik amplifier in real life, it will be very useful to know how they compare to a good AB integrated like the Gryphon, VItus, Pass Labs, T+A, etc. Any pointers?

@blisshifi Thank you for taking the time to form such a detailed reply, it is exactly what I was looking for. I have been using Class D amplifiers for almost 20 years and the technology keeps on improving, IMO they are the future of amplification. It seems like the Achilles heel of the Class D amplifiers (the top end) is becoming less of an issue with the latest generation. Of course regardless of the topology used, the design of the amplifier is the most critical factor. My speakers (Vienna acoustics Mahler) require the amp to have good grip of the bass units and be fast otherwise they can sound lazy, so they work well with class D amplifiers. 

Even though GaN transistors were not designed for the HiFi industry, they could suit class D topology since they are switching much faster (decreasing dead time, easier filter design, etc) but again it all depends in the implementation of the amplifier, you can't say because an amplifier uses GaN transistors is better than one that uses MOSFETs or bipolars, we need to talk about specific amplifiers.

@ricevs I am not familiar with your modifications, the same question as Tjag above, can you describe your modifications and how each one effects the sound of the amplifier? Which amp is your favourite for modding?

@mbmi Do I understand you right that you prefer the Peachtree to the Aavik? Also you are comparing an integrated (the Aavik U-150) to a power amp with a separate preamp. Is there any way to bypass the preamp section of the Aavik and use your Audio_GD with it? Thanks.

@soix  thanks but I can't see a link.

Thanks Soix, I will have a look. I sometimes modify equipment myself but I would not mess about with the circuit topology. Normally I would clean up the mains if needed, sometimes upgrade passive components to better ones (but one has to be very careful, better components in most cases are just unnecessary), perhaps better op-amps and definitely would pay attention to noise especially RF. Unfortunately it is not an easy or even fruitful task, one needs proper test equipment which most moders don't have access to, I am not implying that Ric doesn't know what he is doing! Anyway I diverted...